Fair Value (Details 2) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Oct. 27, 2013	Apr. 28, 2013
Financial assets:
Marketable securities	$ 25,120	$ 25,520
Restricted cash and investments	9,782	11,417
Financial liabilities:
Other long-term obligations	22,433	22,514
Transfers between Level 1 and Level 2 inputs for marketable securities	0
Transfers between Level 1 and Level 2 inputs for restricted cash and investments	0
Level 1
Financial assets:
Marketable securities	8,477	9,433
Restricted cash and investments	4,278	3,979
Level 2
Financial assets:
Marketable securities	16,643	16,087
Restricted cash and investments	5,504	7,438
Carrying Amount
Financial assets:
Cash and cash equivalents	69,958	68,469
Marketable securities	25,120	25,520
Accounts receivable	9,870	11,077
Restricted cash and investments	9,782	11,417
Financial liabilities:
Other long-term obligations	22,433	22,514
Carrying Amount | Revolving line of credit
Financial liabilities:
Long-term debt	160,900	154,900
Carrying Amount | 5.875% Senior notes
Financial liabilities:
Long-term debt	350,000	350,000
Carrying Amount | 7.75% Senior notes
Financial liabilities:
Long-term debt	298,365	298,246
Carrying Amount | 8.875% Senior Subordinated notes
Financial liabilities:
Long-term debt	350,000	350,000
Carrying Amount | Other long-term debt
Financial liabilities:
Long-term debt	3,432	3,738
Fair Value
Financial assets:
Cash and cash equivalents	69,958	68,469
Marketable securities	25,120	25,520
Accounts receivable	9,870	11,077
Restricted cash and investments	9,782	11,417
Financial liabilities:
Other long-term obligations	22,433	22,514
Fair Value | Revolving line of credit
Financial liabilities:
Long-term debt	157,682	151,802
Fair Value | 5.875% Senior notes
Financial liabilities:
Long-term debt	344,750	357,000
Fair Value | 7.75% Senior notes
Financial liabilities:
Long-term debt	319,525	327,698
Fair Value | 8.875% Senior Subordinated notes
Financial liabilities:
Long-term debt	371,000	381,535
Fair Value | Other long-term debt
Financial liabilities:
Long-term debt	$ 3,432	$ 3,738