Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net earnings	$ 98,396	$ 105,588	$ 96,247
Unrealized gains (losses) on securities:
Net unrealized holding gains (losses) arising during period	(39,797)	12,536	(42,218)
Net unrealized liquidity gains (losses)	1,022	26	333
Reclassification adjustment for net amounts included in net earnings	(2,085)	(5,000)	(3,061)
Amortization of net unrealized (gains) losses related to transferred securities	0	0	0
Net unrealized gains (losses) on securities	(40,860)	7,562	(44,946)
Foreign currency translation adjustments	140	(556)	652
Benefit plans:
Amortization of net prior service cost and net gain, net of tax	(737)	(3,300)	5,588
Other comprehensive income (loss)	(41,457)	3,706	(38,706)
Comprehensive income (loss)	$ 56,939	$ 109,294	$ 57,541