Shareholders' Equity Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (36,174)		$ (10,967)		$ 21,587
Reclassification of stranded accumulated other comprehensive loss to retained earnings related to tax reform			(6,550)
Transition adjustment of net unrealized gains on equity securities	2,700		(2,709)
Net change in unrealized gain (loss)	(48,010)		(26,152)		(41,521)
Reclassification adjustments included in earnings: [Abstract]
Interest revenue, Investment securities, Taxable securities	0		0		(112)
Loss (gain) on available for sale securities, net	2,801		(4,428)		(11,675)
Other comprehensive income (loss), before income taxes	(45,209)		(30,580)		(53,308)
Federal and state income taxes	(11,507)	[1]	(11,923)	[2]	(20,754)	[2]
Other comprehensive income (loss), net of income taxes	(33,702)		(18,657)		(32,554)
Ending balance	(72,585)		(36,174)		(10,967)
Unrealized Gain (Loss) on Available for Sale Securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(35,385)		(9,087)		23,284
Reclassification of stranded accumulated other comprehensive loss to retained earnings related to tax reform			(6,408)
Transition adjustment of net unrealized gains on equity securities			(2,709)
Net change in unrealized gain (loss)	(46,941)		(28,170)		(41,333)
Reclassification adjustments included in earnings: [Abstract]
Interest revenue, Investment securities, Taxable securities	0		0		0
Loss (gain) on available for sale securities, net	2,801		(4,428)		(11,675)
Other comprehensive income (loss), before income taxes	(44,140)		(32,598)		(53,008)
Federal and state income taxes	(11,235)	[1]	(12,708)	[2]	(20,637)	[2]
Other comprehensive income (loss), net of income taxes	(32,905)		(19,890)		(32,371)
Ending balance	(70,999)		(35,385)		(9,087)
Unrealized Gain (Loss) on Investment Securities Transferred from AFS [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	0		0		68
Reclassification of stranded accumulated other comprehensive loss to retained earnings related to tax reform			0
Transition adjustment of net unrealized gains on equity securities			0
Net change in unrealized gain (loss)	0		0		0
Reclassification adjustments included in earnings: [Abstract]
Interest revenue, Investment securities, Taxable securities	0		0		(112)
Loss (gain) on available for sale securities, net	0		0		0
Other comprehensive income (loss), before income taxes	0		0		(112)
Federal and state income taxes	0	[1]	0	[2]	(44)	[2]
Other comprehensive income (loss), net of income taxes	0		0		(68)
Ending balance	0		0		0
Unrealized Gain (Loss) on Employee Benefit Plans [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(789)		(1,880)		(1,765)
Reclassification of stranded accumulated other comprehensive loss to retained earnings related to tax reform			(142)
Transition adjustment of net unrealized gains on equity securities			0
Net change in unrealized gain (loss)	(1,069)		2,018		(188)
Reclassification adjustments included in earnings: [Abstract]
Interest revenue, Investment securities, Taxable securities	0		0		0
Loss (gain) on available for sale securities, net	0		0		0
Other comprehensive income (loss), before income taxes	(1,069)		2,018		(188)
Federal and state income taxes	(272)	[1]	785	[2]	(73)	[2]
Other comprehensive income (loss), net of income taxes	(797)		1,233		(115)
Ending balance	$ (1,586)		$ (789)		$ (1,880)

[1] Calculated using a 25 percent blended federal and state statutory tax rate.

[2] Calculated using a 39 percent blended federal and state statutory tax rate.