Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 39,122	$ 26,156	$ 66,099	$ 47,062
Change in securities available-for-sale:
Unrealized holding gains (losses) for the period	12,671	(26,234)	30,528	(7,928)
Reclassification adjustment for securities gains realized in income	(1,856)	(512)	(2,962)	(3,195)
Income tax effect	(3,809)	9,716	(9,977)	3,920
Unrealized gains (losses) on available-for-sale securities	7,006	(17,030)	17,589	(7,203)
Change in securities held-to-maturity:
Amortization of fair value for securities held-to-maturity previously recognized into accumulated other comprehensive income	466	430	931	767
Income tax effect	(159)	(147)	(318)	(81)
Changes from securities held-to-maturity	307	283	613	686
Cash flow hedges:
Net unrealized derivative gains (losses) on cash flow hedges	(4,483)	3,557	(15,613)	(2,071)
Reclassification adjustment for losses realized in net income	1,585	439	2,858	625
Income tax effect	1,101	(1,519)	4,847	549
Changes from cash flow hedges	(1,797)	2,477	(7,908)	(897)
Defined benefit pension plans:
Amortization of net loss recognized in income	730	725	1,430	1,463
Income tax effect	(278)	(275)	(544)	(556)
Changes from defined benefit pension plans	452	450	886	907
Other comprehensive income (loss), net of tax	5,968	(13,820)	11,180	(6,507)
Comprehensive income	$ 45,090	$ 12,336	$ 77,279	$ 40,555