Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net earnings (loss)	$ 62,129	$ (2,062)
Unrealized gains (losses) on securities:
Net unrealized holding gains (losses) arising during period	(152,195)	(78,153)
Net unrealized liquidity gains (losses)	0	1
Reclassification adjustment for net amounts included in net earnings	(1,119)	(601)
Net unrealized gains (losses) on securities	(153,314)	(78,753)
Foreign currency translation adjustments	(5)	(39)
Benefit plans:
Amortization of net prior service cost and net gain (loss)	1,935	(2,066)
Other comprehensive income (loss)	(151,384)	(80,858)
Comprehensive income (loss)	$ (89,255)	$ (82,920)