Marketable Securities (Schedule of Available-for-sale Securities) (Details) - USD ($) $ in Thousands	Sep. 29, 2018	Mar. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 202,098	$ 201,325
Gross Unrealized Gains	3	4
Gross Unrealized Losses	(2,193)	(2,433)
Estimated Fair Value (Net Carrying Amount)	199,908	198,896
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	187,939	185,636
Gross Unrealized Gains	3	4
Gross Unrealized Losses	(2,035)	(2,318)
Estimated Fair Value (Net Carrying Amount)	185,907	183,322
Non-US government securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	13,698	14,730
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(155)	(111)
Estimated Fair Value (Net Carrying Amount)	13,543	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	461	459
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(3)	(4)
Estimated Fair Value (Net Carrying Amount)	$ 458	$ 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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Amortized cost of 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 of 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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