Shareholders' Equity Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (836,955)	$ 72,371	$ 335,868
Net change in unrealized gain (loss)	218,293	(1,227,414)	(341,369)
Transfer of net unrealized loss from AFS to investment securities		0
Reclassification adjustments included in earnings: [Abstract]
Interest revenue, Investment securities	60,394	42,514	0
Operating expense, Personnel		(3,483)
Loss (gain) on available for sale securities, net	30,636	971	(3,704)
Other comprehensive income (loss), before income taxes	309,323	(1,187,412)	(345,073)
Federal and state income taxes	71,468	(278,086)	(81,576)
Other comprehensive income (loss), net of income taxes	237,855	(909,326)	(263,497)
Ending balance	(599,100)	(836,955)	72,371
Unrealized Gain (Loss) on Available for Sale Securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(664,618)	69,775	335,032
Net change in unrealized gain (loss)	218,293	(1,227,414)	(343,730)
Transfer of net unrealized loss from AFS to investment securities		267,509
Reclassification adjustments included in earnings: [Abstract]
Interest revenue, Investment securities	0	0
Operating expense, Personnel		0
Loss (gain) on available for sale securities, net	30,636	971	(3,704)
Other comprehensive income (loss), before income taxes	248,929	(958,934)	(347,434)
Federal and state income taxes	57,523	(224,541)	(82,177)
Other comprehensive income (loss), net of income taxes	191,406	(734,393)	(265,257)
Ending balance	(473,212)	(664,618)	69,775
Accumulated Unrealized Gain/Loss on Investment Securities Transferred from AFS
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(172,337)	0	0
Net change in unrealized gain (loss)	0	0	0
Transfer of net unrealized loss from AFS to investment securities		(267,509)
Reclassification adjustments included in earnings: [Abstract]
Interest revenue, Investment securities	60,394	42,514
Operating expense, Personnel		0
Loss (gain) on available for sale securities, net	0	0	0
Other comprehensive income (loss), before income taxes	60,394	(224,995)	0
Federal and state income taxes	13,945	(52,658)	0
Other comprehensive income (loss), net of income taxes	46,449	(172,337)	0
Ending balance	(125,888)	(172,337)	0
Unrealized Gain (Loss) on Employee Benefit Plans [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	0	2,596	836
Net change in unrealized gain (loss)	0	0	2,361
Transfer of net unrealized loss from AFS to investment securities		0
Reclassification adjustments included in earnings: [Abstract]
Interest revenue, Investment securities	0	0
Operating expense, Personnel		(3,483)
Loss (gain) on available for sale securities, net	0	0	0
Other comprehensive income (loss), before income taxes	0	(3,483)	2,361
Federal and state income taxes	0	(887)	601
Other comprehensive income (loss), net of income taxes	0	(2,596)	1,760
Ending balance	$ 0	$ 0	$ 2,596