Condensed Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statement of Comprehensive Income [Abstract]
Net earnings	$ 28,466	$ 24,782	$ 77,475	$ 68,405
Unrealized gains (losses) on securities:
Net unrealized holding gains (losses) arising during period	(7,793)	(1,833)	14,101	(36,065)
Net unrealized liquidity gains (losses)	(23)	(92)	28	66
Reclassification adjustment for net amounts included in net earnings	(958)	(261)	(3,329)	(2,657)
Amortization of net unrealized (gains) losses related to transferred securities	0	0	0	0
Net unrealized gains (losses) on securities	(8,774)	(2,186)	10,800	(38,656)
Foreign currency translation adjustments	(3)	(38)	(636)	555
Benefit plans:
Amortization of net prior service cost and net gain (loss)	(176)	373	(527)	1,127
Other comprehensive income (loss)	(8,953)	(1,851)	9,637	(36,974)
Comprehensive income (loss)	$ 19,513	$ 22,931	$ 87,112	$ 31,431