Accounts receivable, net Accounts receivable, net Accumulated other comprehensive income Less accumulated depreciation Additional paid-in capital Loss on sale of equity investee CONSOLIDATED BALANCE SHEETS [Abstract] Basic (in dollars per share) Buildings Cash and cash equivalents Beginning of period End of period Interest Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Common stock, authorized (in shares) Common stock, issued (in shares) Common stock, no par value, authorized 120,000,000 shares; 41,910,036 and 41,606,070 shares issued at January 28, 2012 and April 30, 2011, respectively Comprehensive Income Comprehensive Income (Loss) Note [Text Block] Cost of goods sold Costs and estimated earnings in excess of billings Total current liabilities Liabilities, Current CURRENT LIABILITIES: Current maturities of marketing obligations Customer deposits Deferred income taxes, net Deferred Income Taxes, Net, Current Deferred income taxes Deferred income taxes Deferred revenue (billed or collected) Long-term deferred revenue (billed or collected) Derivative Financial Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Diluted (in dollars per share) Equity in losses of affiliates EFFECT OF EXCHANGE RATE CHANGES ON CASH Stock-based compensation Loss (gain) on sale of property and equipment Gross profit Gross Profit Goodwill impairment Impairment of goodwill CONSOLIDATED STATEMENTS OF OPERATIONS [Abstract] Income Taxes Income Tax Disclosure [Text Block] Income taxes, net of refunds Income tax receivables Goodwill Interest expense Interest Expense Inventories Marketable Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Land TOTAL LIABILITIES Liabilities TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY LIABILITIES AND SHAREHOLDERS' EQUITY Marketable securities Marketable Securities [Abstract] Net cash used in financing activities Net Cash Provided by (Used in) Financing Activities CASH FLOWS FROM FINANCING ACTIVITIES: Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities CASH FLOWS FROM INVESTING ACTIVITIES: Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities CASH FLOWS FROM OPERATING ACTIVITIES: Net income Net income NET DECREASE IN CASH AND CASH EQUIVALENTS Recently Issued Accounting Pronouncements [Abstract] Nonoperating income (expense): Total long-term liabilities Liabilities, Noncurrent Long-term receivables, less current maturities Operating income Operating Income (Loss) Change in operating assets and liabilities Other investing activities, net Payments for (Proceeds from) Other Investing Activities Other (expense) income, net Dividends paid Payments of Dividends, Common Stock Insurance recoveries on property and equipment Proceeds from sale of property and equipment Proceeds from exercise of stock options Property and equipment, gross Property, Plant and Equipment, Gross Property and equipment, net Property, Plant and Equipment, Net Provision for doubtful accounts Purchases of marketable securities Payments to Acquire Marketable Securities Purchases of property and equipment Payments to Acquire Property, Plant, and Equipment Principal payments on long-term obligations Repayments of Long-term Debt Restricted cash Retained earnings Net sales Inventories Inventory Disclosure [Text Block] Note 5. Segment Disclosure Segment Reporting Disclosure [Text Block] CONSOLIDATED STATEMENTS OF CASH FLOWS [Abstract] SHAREHOLDERS' EQUITY: Supplemental disclosures of cash flow information: ExcessTaxBenefitFromShareBasedCompensationFinancingActivities Excess tax benefits from stock-based compensation Total current assets Assets, Current CURRENT ASSETS: Diluted (in shares) Basic (in shares) PROPERTY AND EQUIPMENT: TOTAL ASSETS Assets Current maturities of long-term receivables Deferred income taxes Deferred Tax Assets, Net, Noncurrent Machinery and equipment ASSETS Fair Value Measurement Fair Value Disclosures [Text Block] Treasury stock, at cost, 19,680 shares Treasury Stock, Value Operating expenses: Earnings per share: Earnings Per Share EPS [Abstract] Treasury stock, shares (in shares) TOTAL SHAREHOLDERS' EQUITY Stockholders' Equity Attributable to Parent Income tax expense Purchase of property and equipment included in accounts payable Common stock, no par value (in dollars per share) Earnings Per Share EPS Earnings Per Share [Text Block] Weighted average shares outstanding: Income tax payable Adjustments to reconcile net income (loss) to net cash provided by operating activities: Adjustments to reconcile net income to net cash provided by operating activities: Accounts payable Investments in Affiliates Investments in and Advances to Affiliates, Schedule of Investments [Text Block] Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest Prepaid expenses and other assets Billings in excess of costs and estimated earnings Receivables Financing Receivables [Text Block] Basis of Presentation and Summary of Critical Accounting Policies Basis of Presentation and Significant Accounting Policies [Text Block] CASH AND CASH EQUIVALENTS: Receivables [Abstract] Receivables Commitments and Contingencies [Abstract] Income Taxes [Abstract] Goodwill [Abstract] Fair Value Measurement [Abstract] Inventories [Abstract] Investments in Affiliates [Abstract] Goodwill Goodwill Disclosure [Text Block] Derivative Financial Instruments [Abstract] Segment Disclosure [Abstract] Supplemental schedule of non-cash investing and financing activities: Amendment Flag Current Fiscal Year End Date Document Period End Date Entity [Text Block] Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Current Reporting Status Entity Filer Category Entity Public Float Entity Registrant Name Entity Central Index Key Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Period Focus Document Type Noncurrent Assets Excluding Property Plant and Equipment Sum of the carrying amounts as of the balance sheet date of all assets excluding property, plant, and equipment that are expected to be realized in cash, sold or consumed after one year or beyond the normal operating cycle, if longer. Total noncurrent assets CONSOLIDATED BALANCE SHEETS - Parenthetical [Abstract] CONSOLIDATED BALANCE SHEETS (Parenthetical) [Abstract] Demonstration equipment Gross amount, as of the balance sheet date, of long-lived, depreciable equipment used for demonstration. Transportation equipment Gross amount, as of the balance sheet date, of long-lived, depreciable equipment used for transportation. Cash payments for: [Abstract] Cash payments for: Demonstration equipment transferred to inventory Value of demonstration equipment transferred to inventory in noncash transaction during the reporting period. Basis of Presentation and Summary of Critical Accounting Policies [Abstract] Equipment held for rental Gross amount, as of the balance sheet date, of long-lived, depreciable equipment held for rental. Comprehensive Income [Abstract] Short term bank loans and notes payable Notes payable, bank Deferred Tax Liabilities, Current Deferred income taxes Sales or maturities of marketable securities Proceeds from lines of credit Borrowings on notes payable AdvertisingRightsNetAndOther Cost of equipment is recorded as advertising rights where advertising agreements have not sold for the full value of the equipment at normal margins, reported on the balance sheet as noncurrent assets, and other assets not otherwise specified in the taxonomy. Advertising rights, net and other assets FiniteLivedIntangibleAssetsNet Intangibles FurnitureAndFixturesGross Office furniture and equipment CapitalizedComputerSoftwareAndEquipmentGross Gross amount, at the balance sheet date, capitalized computer software and equipment costs. Computer software and hardware ProductWarrantyAccrualClassifiedCurrent Warranty obligations ProductWarrantyAccrualNoncurrent Long-term warranty obligations AccretionAmortizationOfDiscountsAndPremiumsInvestments Amortization of premium/discount on marketable securities Subsequent Event ScheduleOfSubsequentEventsTextBlock Subsequent Events Excess Tax Benefit from Share-based Compensation, Operating Activities Excess tax benefits from stock-based compensation Selling expense Research and Development Expense Product design and development General and administrative General and Administrative Expense Total operating expenses Operating Expenses Accrued Liabilities, Current Accrued expenses Investment Income, Net Interest income Common Stock, Dividends, Per Share, Cash Paid Cash dividend paid per share (in dollars per share) Other Liabilities, Noncurrent Other long-term obligations, less current maturities Other Depreciation and Amortization Depreciation and amortization AccruedExpenses Carrying values as of the balance sheet date of obligations incurred and payable for obligations related to services received from employees, costs that are statutory in nature, or incurred on contractual obligations. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). OtherLongTermDebtNoncurrentAndOtherPayables Carrying value as of the balance sheet date of debt not otherwise defined (with maturities initially due after one year or beyond the operating cycle if longer) and other liabilities not separately disclosed in the balance sheet, excluding current portion. Investment income net amortization of discount and premium Describes disclosed significant events or transactions that occurred after the balance sheet date, but before the issuance of the financial statements. Examples include: the sale of a capital stock issue, purchase of a business, settlement of litigation, losses resulting from fire or flood, losses on receivables, significant realized and unrealized gains and losses that result from changes in quoted market prices of securities, declines in market prices of inventory, changes in authorized or issued debt (SEC), significant foreign exchange rate changes, substantial loans to insiders or affiliates, significant long-term investments, and substantial dividends not in the ordinary course of business.