Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Equity [Abstract]
Deferred costs	$ 187,987	$ (304,955)	$ (85,609)
Amounts Before Taxes
Net unrealized holding gains (losses) arising during the period	(227,325)	446,280	122,726
Unrealized liquidity gains (losses)		8	4
Reclassification adjustment for net (gains) losses included in net earnings	(16,372)	(5,677)	5,060
Net unrealized gains (losses) on securities	(243,697)	440,611	127,790
Foreign currency translation adjustments	(20)	18	663
Benefit plan liability adjustment	16,543	(16,182)	(5,513)
Other comprehensive income (loss)	(227,174)	424,447	122,940
Tax (Expense) Benefit
Net unrealized holding gains (losses) arising during the period	47,738	(93,719)	(25,772)
Unrealized liquidity gains (losses)		(2)	(1)
Reclassification adjustment for net (gains) losses included in net earnings	3,438	1,192	(1,063)
Net unrealized gains (losses) on securities	51,176	(92,529)	(26,836)
Foreign currency translation adjustments	4	(4)	(139)
Benefit plan liability adjustment	(3,474)	3,398	1,158
Other comprehensive income (loss)	47,706	(89,135)	(25,817)
Amounts Net of Taxes
Net unrealized holding gains (losses) arising during the period	(179,587)	352,561	96,954
Unrealized liquidity gains (losses)	0	6	3
Reclassification adjustment for net (gains) losses included in net earnings	(12,934)	(4,485)	3,997
Net unrealized gains (losses) on securities	(192,521)	348,082	100,954
Foreign currency translation adjustments	(16)	14	524
Benefit plan liability adjustment	13,069	(12,784)	(4,355)
Other comprehensive income (loss)	$ (179,468)	$ 335,312	$ 97,123