Financial Instruments (Details 1) - USD ($) $ in Thousands	Sep. 26, 2015	Mar. 28, 2015
Fair values and gross unrealized losses of the investments
Available-for-Sale Securities, Less Than 12 Months, Fair Value	$ 845,489	$ 1,095,972
Available-for-Sale Securities, Less Than 12 Months, Gross Unrealized Losses	(10,736)	(5,009)
Available-for-Sale Securities, 12 Months or Greater, Fair Value	156,859	118,042
Available-for-Sale Securities, 12 Months or Greater, Gross Unrealized Losses	(9,159)	(6,331)
Available-for-Sale Securities, Fair Value, Total	1,002,348	1,214,014
Available-for-Sale Securities, Gross Unrealized Losses, Total	(19,895)	(11,340)
Non-financial institution securities [Member]
Fair values and gross unrealized losses of the investments
Available-for-Sale Securities, Less Than 12 Months, Fair Value	65,885	7,190
Available-for-Sale Securities, Less Than 12 Months, Gross Unrealized Losses	(232)	(6)
Available-for-Sale Securities, 12 Months or Greater, Fair Value	0	0
Available-for-Sale Securities, 12 Months or Greater, Gross Unrealized Losses	0	0
Available-for-Sale Securities, Fair Value, Total	65,885	7,190
Available-for-Sale Securities, Gross Unrealized Losses, Total	(232)	(6)
Auction Rate Securities [Member]
Fair values and gross unrealized losses of the investments
Available-for-Sale Securities, Less Than 12 Months, Fair Value	0	0
Available-for-Sale Securities, Less Than 12 Months, Gross Unrealized Losses	0	0
Available-for-Sale Securities, 12 Months or Greater, Fair Value	10,414	10,312
Available-for-Sale Securities, 12 Months or Greater, Gross Unrealized Losses	(87)	(188)
Available-for-Sale Securities, Fair Value, Total	10,414	10,312
Available-for-Sale Securities, Gross Unrealized Losses, Total	(87)	(188)
Municipal Bonds [Member]
Fair values and gross unrealized losses of the investments
Available-for-Sale Securities, Less Than 12 Months, Fair Value	24,204	10,014
Available-for-Sale Securities, Less Than 12 Months, Gross Unrealized Losses	(107)	(94)
Available-for-Sale Securities, 12 Months or Greater, Fair Value	2,407	1,931
Available-for-Sale Securities, 12 Months or Greater, Gross Unrealized Losses	(139)	(58)
Available-for-Sale Securities, Fair Value, Total	26,611	11,945
Available-for-Sale Securities, Gross Unrealized Losses, Total	(246)	(152)
U.S. Government and Agency Securities [Member]
Fair values and gross unrealized losses of the investments
Available-for-Sale Securities, Less Than 12 Months, Fair Value	63,640	451,296
Available-for-Sale Securities, Less Than 12 Months, Gross Unrealized Losses	(7)	(129)
Available-for-Sale Securities, 12 Months or Greater, Fair Value	0	0
Available-for-Sale Securities, 12 Months or Greater, Gross Unrealized Losses	0	0
Available-for-Sale Securities, Fair Value, Total	63,640	451,296
Available-for-Sale Securities, Gross Unrealized Losses, Total	(7)	(129)
Mortgage-Backed Securities [Member]
Fair values and gross unrealized losses of the investments
Available-for-Sale Securities, Less Than 12 Months, Fair Value	471,040	448,770
Available-for-Sale Securities, Less Than 12 Months, Gross Unrealized Losses	(3,681)	(3,169)
Available-for-Sale Securities, 12 Months or Greater, Fair Value	52,141	49,207
Available-for-Sale Securities, 12 Months or Greater, Gross Unrealized Losses	(1,164)	(1,327)
Available-for-Sale Securities, Fair Value, Total	523,181	497,977
Available-for-Sale Securities, Gross Unrealized Losses, Total	(4,845)	(4,496)
Asset-backed Securities [Member]
Fair values and gross unrealized losses of the investments
Available-for-Sale Securities, Less Than 12 Months, Fair Value	72,972	75,009
Available-for-Sale Securities, Less Than 12 Months, Gross Unrealized Losses	(479)	(159)
Available-for-Sale Securities, 12 Months or Greater, Fair Value	9,631	0
Available-for-Sale Securities, 12 Months or Greater, Gross Unrealized Losses	(44)	0
Available-for-Sale Securities, Fair Value, Total	82,603	75,009
Available-for-Sale Securities, Gross Unrealized Losses, Total	(523)	(159)
Debt Mutual Fund [Member]
Fair values and gross unrealized losses of the investments
Available-for-Sale Securities, Less Than 12 Months, Fair Value	34,650	38,608
Available-for-Sale Securities, Less Than 12 Months, Gross Unrealized Losses	(5,350)	(1,392)
Available-for-Sale Securities, 12 Months or Greater, Fair Value	53,671	56,592
Available-for-Sale Securities, 12 Months or Greater, Gross Unrealized Losses	(7,679)	(4,758)
Available-for-Sale Securities, Fair Value, Total	88,321	95,200
Available-for-Sale Securities, Gross Unrealized Losses, Total	(13,029)	(6,150)
Bank Loans [Member]
Fair values and gross unrealized losses of the investments
Available-for-Sale Securities, Less Than 12 Months, Fair Value	42,444	65,085
Available-for-Sale Securities, Less Than 12 Months, Gross Unrealized Losses	(61)	(60)
Available-for-Sale Securities, 12 Months or Greater, Fair Value	28,253	0
Available-for-Sale Securities, 12 Months or Greater, Gross Unrealized Losses	(32)	0
Available-for-Sale Securities, Fair Value, Total	70,697	65,085
Available-for-Sale Securities, Gross Unrealized Losses, Total	(93)	$ (60)
Commercial Mortgage Backed Securities [Member]
Fair values and gross unrealized losses of the investments
Available-for-Sale Securities, Less Than 12 Months, Fair Value	70,654
Available-for-Sale Securities, Less Than 12 Months, Gross Unrealized Losses	(819)
Available-for-Sale Securities, 12 Months or Greater, Fair Value	342
Available-for-Sale Securities, 12 Months or Greater, Gross Unrealized Losses	(14)
Available-for-Sale Securities, Fair Value, Total	70,996
Available-for-Sale Securities, Gross Unrealized Losses, Total	$ (833)