Investments (Unrealized Loss) (Details) - USD ($) $ in Thousands	Sep. 27, 2015	Mar. 29, 2015
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Fair Value Less than 12 months	$ 210,703	$ 105,588
Unrealized Loss Less than 12 months	(407)	(159)
Fair Value 12 months or Greater	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Fair Value Total	210,703	105,588
Unrealized Loss Total	(407)	(159)
Corporate bonds
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Fair Value Less than 12 months	151,943	67,367
Unrealized Loss Less than 12 months	(366)	(121)
Fair Value 12 months or Greater	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Fair Value Total	151,943	67,367
Unrealized Loss Total	(366)	(121)
Asset-backed securities
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Fair Value Less than 12 months	17,306	17,736
Unrealized Loss Less than 12 months	(17)	(9)
Fair Value 12 months or Greater	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Fair Value Total	17,306	17,736
Unrealized Loss Total	(17)	(9)
U.S. government treasuries and agencies securities
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Fair Value Less than 12 months	38,447	18,478
Unrealized Loss Less than 12 months	(18)	(23)
Fair Value 12 months or Greater	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Fair Value Total	38,447	18,478
Unrealized Loss Total	(18)	(23)
Municipal bonds
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Fair Value Less than 12 months	2,003	1,001
Unrealized Loss Less than 12 months	(3)	(2)
Fair Value 12 months or Greater	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Fair Value Total	2,003	1,001
Unrealized Loss Total	(3)	(2)
International government bonds
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Fair Value Less than 12 months	1,004	1,006
Unrealized Loss Less than 12 months	(3)	(4)
Fair Value 12 months or Greater	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Fair Value Total	1,004	1,006
Unrealized Loss Total	$ (3)	$ (4)