Consolidated Statements of Comprehensive Earnings (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net earnings	$ 74,225	$ 68,369	$ 59,659
OTHER ITEMS OF COMPREHENSIVE EARNINGS:
Change in unrealized gain (loss) on investment securities available-for-sale, before income tax	10,619	44,279	(15,332)
Reclassification adjustment for realized gains on investment securities included in net earnings, before income tax	(2,772)	(492)	(363)
Minimum liability pension adjustment, before income tax	(1,564)	(2,599)	(650)
Total other items of comprehensive earnings	6,283	41,188	(16,345)
Income tax benefit (expense) related to:
Investment securities	(2,746)	(15,325)	5,493
Minimum liability pension adjustment	547	909	227
Income tax expense related to other items of comprehensive earnings	(2,199)	(14,416)	5,720
COMPREHENSIVE EARNINGS	$ 78,309	$ 95,141	$ 49,034