CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 50,065	$ 39,027	$ 96,160	$ 75,214
Unrealized gains and losses on available for sale securities
Net gains (losses) arising during the period	1,896	(635)	3,203	7,648
Less reclassification adjustment for net (gains) losses included in net income	(13)	2	0	(168)
Total	1,883	(633)	3,203	7,480
Non-credit impairment losses on available for sale securities
Net change in non-credit impairment losses on securities	21	301	134	242
Less reclassification adjustment for accretion of credit impairment losses included in net income	(39)	0	(126)	(286)
Total	(18)	301	8	(44)
Unrealized gains and losses on derivatives (cash flow hedges)
Net losses on derivatives arising during the period	(873)	(2,122)	(746)	(8,674)
Less reclassification adjustment for net losses included in net income	1,356	2,107	2,831	3,848
Total	483	(15)	2,085	(4,826)
Defined benefit pension plan
Amortization of net loss	59	43	118	86
Total other comprehensive income	2,407	(304)	5,414	2,696
Total comprehensive income	$ 52,472	$ 38,723	$ 101,574	$ 77,910