CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012	Jun. 30, 2012		Sep. 30, 2011	Sep. 30, 2012		Sep. 30, 2011
Net earnings	$ 16,088	$ 15,557		$ 13,304	$ 36,909		$ 36,821
Other comprehensive income related to securities available-for-sale:
Unrealized holding gains arising during the period	12,966	8,185		22,218	28,560		33,372
Income tax expense related to unrealized holding gains arising during the period	(5,445)	(3,439)		(9,332)	(11,995)		(14,017)
Reclassification adjustment for loss included in net earnings		1,115	[1]		1,115	[1]
Income tax benefit related to reclassification adjustment		(468)			(468)
Other comprehensive income	7,521	5,393		12,886	17,212		19,355
Comprehensive income	$ 23,609	$ 20,950		$ 26,190	$ 54,121		$ 56,176

[1] Included in "Other-than-temporary impairment loss on covered security" on condensed consolidated statements of earnings.