Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 23,284	$ 18,549	$ 65,740	$ 54,713
Unrealized holding gains (losses):
Before tax	6,126	(2,693)	748	22,028
Tax effect	(2,454)	1,003	(312)	(8,776)
Net of tax	3,672	(1,690)	436	13,252
Reclassification of net gains included in net income:
Before tax	524	2,570	1,551	8,160
Tax effect	(214)	(1,051)	(634)	(3,337)
Net of tax	310	1,519	917	4,823
Net unrealized holding gains (losses)	3,362	(3,209)	(481)	8,429
Derivative instruments
Before tax	3,420	(629)	870	(827)
Tax effect	(1,368)	257	(352)	338
Net of tax	2,052	(372)	518	(489)
Total other comprehensive income (loss)	5,414	(3,581)	37	7,940
Total comprehensive income	$ 28,698	$ 14,968	$ 65,777	$ 62,653