Marketable Securities (Schedule of Available-for-sale Securities) (Details) - USD ($) $ in Thousands	Dec. 29, 2018	Mar. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 226,501	$ 201,325
Gross Unrealized Gains	144	4
Gross Unrealized Losses	(1,789)	(2,433)
Estimated Fair Value (Net Carrying Amount)	224,856	198,896
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	212,338	185,636
Gross Unrealized Gains	142	4
Gross Unrealized Losses	(1,703)	(2,318)
Estimated Fair Value (Net Carrying Amount)	210,777	183,322
Non-US government securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	13,704	14,730
Gross Unrealized Gains	2	0
Gross Unrealized Losses	(84)	(111)
Estimated Fair Value (Net Carrying Amount)	13,622	14,619
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		500
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Estimated Fair Value (Net Carrying Amount)		500
Agency discount notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	459	459
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(2)	(4)
Estimated Fair Value (Net Carrying Amount)	$ 457	$ 455

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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