Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 30, 2019	Mar. 31, 2018
Available-for-sale securities
Amortized Cost	$ 3,096,631	$ 3,406,976
Available-for-sale Securities, Gross Unrealized Gains (Instant)	893	678
Available-for-sale Securities, Gross Unrealized Losses (Instant)	(17,437)	(28,764)
Estimated Fair Value	3,080,087	3,378,890
Money Market Funds [Member]
Available-for-sale securities
Amortized Cost	428,150	1,291,891
Available-for-sale Securities, Gross Unrealized Gains (Instant)	0	0
Available-for-sale Securities, Gross Unrealized Losses (Instant)	0	0
Estimated Fair Value	428,150	1,291,891
Financial institution securities [Member]
Available-for-sale securities
Amortized Cost	537,795	434,901
Available-for-sale Securities, Gross Unrealized Gains (Instant)	0	0
Available-for-sale Securities, Gross Unrealized Losses (Instant)	0	0
Estimated Fair Value	537,795	434,901
Non-financial institution securities [Member]
Available-for-sale securities
Amortized Cost	702,483	326,219
Available-for-sale Securities, Gross Unrealized Gains (Instant)	3	0
Available-for-sale Securities, Gross Unrealized Losses (Instant)	(562)	(1,376)
Estimated Fair Value	701,924	324,843
U.S. Government and Agency Securities [Member]
Available-for-sale securities
Amortized Cost	334,185	58,913
Available-for-sale Securities, Gross Unrealized Gains (Instant)	39	1
Available-for-sale Securities, Gross Unrealized Losses (Instant)	(139)	(272)
Estimated Fair Value	334,085	58,642
Foreign Government and Agency Securities [Member]
Available-for-sale securities
Amortized Cost	214,455	179,957
Available-for-sale Securities, Gross Unrealized Gains (Instant)	0	0
Available-for-sale Securities, Gross Unrealized Losses (Instant)	0	0
Estimated Fair Value	214,455	179,957
Mortgage-Backed Securities [Member]
Available-for-sale securities
Amortized Cost	684,596	866,048
Available-for-sale Securities, Gross Unrealized Gains (Instant)	809	660
Available-for-sale Securities, Gross Unrealized Losses (Instant)	(14,635)	(22,311)
Estimated Fair Value	670,770	844,397
Asset-backed Securities [Member]
Available-for-sale securities
Amortized Cost	76,852	92,751
Available-for-sale Securities, Gross Unrealized Gains (Instant)	0	16
Available-for-sale Securities, Gross Unrealized Losses (Instant)	(483)	(1,378)
Estimated Fair Value	76,369	91,389
Commercial Mortgage Backed Securities [Member]
Available-for-sale securities
Amortized Cost	118,115	156,296
Available-for-sale Securities, Gross Unrealized Gains (Instant)	42	1
Available-for-sale Securities, Gross Unrealized Losses (Instant)	(1,618)	(3,427)
Estimated Fair Value	$ 116,539	$ 152,870