Stock Incentive and Purchase Plans (Allocation of Share Based Compensation Costs by Expense Category) (Details) (USD $)	12 Months Ended
	Apr. 26, 2013	Apr. 27, 2012	Apr. 29, 2011
Employee Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 11,683,249	$ 11,102,237	$ 6,365,003
Income tax benefit related to awards recognized in the consolidated statements of income	3,810,136	3,461,453	1,992,308
Total expense, net of income tax benefit	7,873,113	7,640,784	4,372,695
Cost of goods sold [Member]
Employee Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	504,715	578,157	452,106
Selling, general and administrative [Member]
Employee Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	7,949,517	8,106,663	4,784,081
Research and development [Member]
Employee Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 3,229,017	$ 2,417,417	$ 1,128,816