Stock Incentive and Purchase Plans (Allocation of Share Based Compensation Costs by Type of Arrangement) (Details) (USD $)	3 Months Ended
	Jul. 26, 2013	Jul. 27, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 3,153,499	$ 4,406,533
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	970,018	875,218
Service-based restricted stock and restricted stock unit awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	1,486,595	1,975,803
Performance-based restricted stock and restricted stock unit and market-based awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 696,886	$ 1,555,512