Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Statement of Comprehensive Income [Abstract]
Net earnings	$ 30,765	$ 49,899	$ 66,949	$ 112,028
Unrealized gains (losses) on available-for-sale securities:
Net unrealized holding gains (losses) arising during period	(232,914)	41,396	(509,523)	(110,799)
Reclassification adjustment for net amounts included in net earnings	(1,395)	(3,810)	(4,127)	(4,929)
Net unrealized gains (losses) on securities	(234,309)	37,586	(513,650)	(115,728)
Foreign currency translation adjustments	(22)	(71)	291	(76)
Benefit plans:
Amortization of net prior service cost and net gain	1,134	1,935	2,268	3,870
Other comprehensive income (loss)	(233,197)	39,450	(511,091)	(111,934)
Comprehensive income (loss)	$ (202,432)	$ 89,349	$ (444,142)	$ 94