Marketable Securities (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 29, 2012	Mar. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses	$ 4	$ 39
Amortized costs	66,706	118,783
12 Different Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses	4
Amortized costs	25,500
Number of securities	12
37 Different Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses		39
Amortized costs		$ 72,600
Number of securities		37