Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net earnings	$ (2,062)	$ 40,198
Unrealized gains (losses) on securities:
Net unrealized holding gains (losses) arising during period	(78,153)	42,743
Net unrealized liquidity gains (losses)	1	1
Reclassification adjustment for net amounts included in net earnings	(601)	(868)
Net unrealized gains (losses) on securities	(78,753)	41,876
Foreign currency translation adjustments	(39)	553
Benefit plans:
Amortization of net prior service cost and net gain (loss)	(2,066)	(504)
Other comprehensive income (loss)	(80,858)	41,925
Comprehensive income (loss)	$ (82,920)	$ 82,123