Investments - Available-for-Sale (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Apr. 01, 2018
Debt Securities, Available-for-sale [Line Items]
Cost	$ 320,216
Estimated Fair Value	192,032	$ 222,026
U.S. government treasuries and agencies securities
Debt Securities, Available-for-sale [Line Items]
Cost	61,203	61,166
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(845)	(894)
Estimated Fair Value	60,358	60,272
Money market funds
Debt Securities, Available-for-sale [Line Items]
Cost	101,034	48,847
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	101,034	48,847
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Cost	13,931	16,797
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(68)	(110)
Estimated Fair Value	13,863	16,687
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Cost	109,327	111,266
Gross Unrealized Gains	41	43
Gross Unrealized Losses	(1,504)	(1,704)
Estimated Fair Value	107,864	109,605
International government bonds
Debt Securities, Available-for-sale [Line Items]
Cost	0	2,650
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	(12)
Estimated Fair Value	0	2,638
Corporate commercial paper
Debt Securities, Available-for-sale [Line Items]
Cost	17,402	9,034
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	17,402	9,034
Bank deposits
Debt Securities, Available-for-sale [Line Items]
Cost	17,216	45,080
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	17,216	45,080
Repurchase agreements
Debt Securities, Available-for-sale [Line Items]
Cost	103	142
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	103	142
Total available-for-sale investments
Debt Securities, Available-for-sale [Line Items]
Cost	320,216	294,982
Gross Unrealized Gains	41	43
Gross Unrealized Losses	(2,417)	(2,720)
Estimated Fair Value	317,840	292,305
Less amounts classified as cash equivalents
Debt Securities, Available-for-sale [Line Items]
Cost	125,808	70,279
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	125,808	70,279
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Cost	194,408	224,703
Gross Unrealized Gains	41	43
Gross Unrealized Losses	(2,417)	(2,720)
Estimated Fair Value	$ 192,032	$ 222,026

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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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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