Marketable Securities (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 29, 2012	Mar. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses	$ 16	$ 39
Amortized costs	60,720	118,783
Fifteen Different Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses	16
Amortized costs	23,600
Number of securities	15
37 Different Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses		39
Amortized costs		$ 72,600
Number of securities		37