Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Equity [Abstract]
Deferred costs	$ (473,867)	$ 187,987	$ (304,955)
Amounts Before Taxes
Net unrealized holding gains (losses) arising during the period	(812,846)	(227,325)	446,280
Unrealized liquidity gains (losses)			8
Reclassification adjustment for net (gains) losses included in net earnings	(5,111)	(16,372)	(5,677)
Net unrealized gains (losses) on securities	(817,957)	(243,697)	440,611
Foreign currency translation adjustments	515	(20)	18
Benefit plan liability adjustment	16,997	16,543	(16,182)
Other comprehensive income (loss)	(800,445)	(227,174)	424,447
Tax (Expense) Benefit
Net unrealized holding gains (losses) arising during the period	170,698	47,738	(93,719)
Unrealized liquidity gains (losses)			(2)
Reclassification adjustment for net (gains) losses included in net earnings	1,073	3,438	1,192
Net unrealized gains (losses) on securities	171,771	51,176	(92,529)
Foreign currency translation adjustments	(108)	4	(4)
Benefit plan liability adjustment	(3,569)	(3,474)	3,398
Other comprehensive income (loss)	168,094	47,706	(89,135)
Amounts Net of Taxes
Net unrealized holding gains (losses) arising during the period	(642,148)	(179,587)	352,561
Unrealized liquidity gains (losses)	0	0	6
Reclassification adjustment for net (gains) losses included in net earnings	(4,038)	(12,934)	(4,485)
Net unrealized gains (losses) on securities	(646,186)	(192,521)	348,082
Foreign currency translation adjustments	407	(16)	14
Benefit plan liability adjustment	13,428	13,069	(12,784)
Other comprehensive income (loss)	$ (632,351)	$ (179,468)	$ 335,312