Shareholders' Equity Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 335,868	$ 104,923	$ (72,585)
Net change in unrealized gain (loss)	(341,369)	313,796	241,047
Reclassification adjustments included in earnings: [Abstract]
Gain on available for sale securities, net	(3,704)	(9,910)	(5,597)
Other comprehensive income (loss), before income taxes	(345,073)	303,886	235,450
Federal and state income taxes	(81,576)	72,941	57,942
Other comprehensive income (loss), net of income taxes	(263,497)	230,945	177,508
Ending balance	72,371	335,868	104,923
Unrealized Gain (Loss) on Available for Sale Securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	335,032	104,996	(70,999)
Net change in unrealized gain (loss)	(343,730)	312,576	239,017
Reclassification adjustments included in earnings: [Abstract]
Gain on available for sale securities, net	(3,704)	(9,910)	(5,597)
Other comprehensive income (loss), before income taxes	(347,434)	302,666	233,420
Federal and state income taxes	(82,177)	72,630	57,425
Other comprehensive income (loss), net of income taxes	(265,257)	230,036	175,995
Ending balance	69,775	335,032	104,996
Unrealized Gain (Loss) on Employee Benefit Plans [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	836	(73)	(1,586)
Net change in unrealized gain (loss)	2,361	1,220	2,030
Reclassification adjustments included in earnings: [Abstract]
Gain on available for sale securities, net	0	0	0
Other comprehensive income (loss), before income taxes	2,361	1,220	2,030
Federal and state income taxes	601	311	517
Other comprehensive income (loss), net of income taxes	1,760	909	1,513
Ending balance	$ 2,596	$ 836	$ (73)