Fair Value Of Financial Instruments (Narrative) (Details) (USD $)	3 Months Ended
	Jun. 25, 2011	Mar. 26, 2011
Cash and cash equivalents and restricted investments	$ 47,200,000
Minimum maturity period of investments to be classified as available for sale securities, days	90
Gross unrealized losses	30,000	47,000
Amortized costs	108,329,000	172,214,000
Fair Value, Inputs, Level 1 [Member]
Short and long-term investments	108,400,000
Ten Different Securities [Member]
Gross unrealized losses	30,000
Amortized costs	21,500,000
Number of securities	10
Twenty Eight Different Securities [Member]
Gross unrealized losses		47,000
Amortized costs		$ 61,800,000
Number of securities		28