Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net earnings	$ 17,259	$ 21,326
Unrealized gains (losses) on securities:
Net unrealized holding gains (losses) arising during period	24,646	9,372
Net unrealized liquidity gains (losses)	9	61
Reclassification adjustment for net amounts included in net earnings	(460)	(165)
Net unrealized gains (losses) on securities	24,195	9,268
Foreign currency translation adjustments	99	41
Benefit plans:
Amortization of net prior service cost and net gain (loss)	(283)	(303)
Other comprehensive income (loss)	24,011	9,006
Comprehensive income (loss)	$ 41,270	$ 30,332