Marketable Securities - Schedule of Available-for-Sale Securities (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 29, 2013	Mar. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	$ 345,972	$ 357,608
Available-for-sale securities, Gross Unrealized Gains	1,397	2,441
Available-for-sale securities, Gross Unrealized Losses	(868)	(75)
Available-for-sale securities, Estimated Fair Value	346,501	359,974
U.S. government and agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	83,424	113,033
Available-for-sale securities, Gross Unrealized Gains	98	327
Available-for-sale securities, Gross Unrealized Losses	(163)	(1)
Available-for-sale securities, Estimated Fair Value	83,359	113,359
Corporate debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	166,190	153,460
Available-for-sale securities, Gross Unrealized Gains	1,027	1,429
Available-for-sale securities, Gross Unrealized Losses	(162)	(30)
Available-for-sale securities, Estimated Fair Value	167,055	154,859
Mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	52,583	50,852
Available-for-sale securities, Gross Unrealized Gains	210	473
Available-for-sale securities, Gross Unrealized Losses	(406)	(44)
Available-for-sale securities, Estimated Fair Value	52,387	51,281
Municipal bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	41,079	39,661
Available-for-sale securities, Gross Unrealized Gains	62	211
Available-for-sale securities, Gross Unrealized Losses	(134)
Available-for-sale securities, Estimated Fair Value	41,007	39,872
Other debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost	2,696	602
Available-for-sale securities, Gross Unrealized Gains		1
Available-for-sale securities, Gross Unrealized Losses	(3)
Available-for-sale securities, Estimated Fair Value	$ 2,693	$ 603