Financial Instruments (Details 1) - USD ($) $ in Thousands	3 Months Ended
	Jun. 29, 2019	Mar. 30, 2019
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Equity Securities, Gross Unrealized Loss	$ 1,400
Available-for-Sale Securities, Less Than 12 Months, Fair Value	54,280	$ 40,716
Available-for-Sale Securities, Less Than 12 Months, Gross Unrealized Losses	(167)	(487)
Available-for-Sale Securities, 12 Months or Greater, Fair Value	567,526	850,377
Available-for-Sale Securities, 12 Months or Greater, Gross Unrealized Losses	(5,928)	(16,950)
Available-for-Sale Securities, Fair Value, Total	621,806	891,093
Available-for-Sale Securities, Gross Unrealized Losses, Total	(6,095)	(17,437)
Non-financial institution securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Securities, Less Than 12 Months, Fair Value	0	4,767
Available-for-Sale Securities, Less Than 12 Months, Gross Unrealized Losses	0	(4)
Available-for-Sale Securities, 12 Months or Greater, Fair Value	38,010	51,044
Available-for-Sale Securities, 12 Months or Greater, Gross Unrealized Losses	(176)	(558)
Available-for-Sale Securities, Fair Value, Total	38,010	55,811
Available-for-Sale Securities, Gross Unrealized Losses, Total	(176)	(562)
U.S. Government and Agency Securities [Member]
Debt Securities, Available-for-sale [Line Items]
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	13,633	13,542
Available-for-Sale Securities, 12 Months or Greater, Gross Unrealized Losses	(47)	(139)
Available-for-Sale Securities, Fair Value, Total	13,633	13,542
Available-for-Sale Securities, Gross Unrealized Losses, Total	(47)	(139)
Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Securities, Less Than 12 Months, Fair Value	40,762	34,595
Available-for-Sale Securities, Less Than 12 Months, Gross Unrealized Losses	(148)	(480)
Available-for-Sale Securities, 12 Months or Greater, Fair Value	411,450	597,394
Available-for-Sale Securities, 12 Months or Greater, Gross Unrealized Losses	(5,018)	(14,155)
Available-for-Sale Securities, Fair Value, Total	452,212	631,989
Available-for-Sale Securities, Gross Unrealized Losses, Total	(5,166)	(14,635)
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Securities, Less Than 12 Months, Fair Value	6,458	0
Available-for-Sale Securities, Less Than 12 Months, Gross Unrealized Losses	(3)	0
Available-for-Sale Securities, 12 Months or Greater, Fair Value	35,955	76,103
Available-for-Sale Securities, 12 Months or Greater, Gross Unrealized Losses	(110)	(483)
Available-for-Sale Securities, Fair Value, Total	42,413	76,103
Available-for-Sale Securities, Gross Unrealized Losses, Total	(113)	(483)
Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Securities, Less Than 12 Months, Fair Value	7,060	1,354
Available-for-Sale Securities, Less Than 12 Months, Gross Unrealized Losses	(16)	(3)
Available-for-Sale Securities, 12 Months or Greater, Fair Value	68,478	112,294
Available-for-Sale Securities, 12 Months or Greater, Gross Unrealized Losses	(577)	(1,615)
Available-for-Sale Securities, Fair Value, Total	75,538	113,648
Available-for-Sale Securities, Gross Unrealized Losses, Total	$ (593)	$ (1,618)