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	$ 39,027	$ 31,991	$ 75,214	$ 62,332
Other comprehensive (loss) income, net of tax:
Net (losses) gains arising during the period	(635)	(5,845)	7,648	(1,909)
Less reclassification adjustment for net losses (gains) included in net income	2	55	(168)	(1,354)
Total	(633)	(5,790)	7,480	(3,263)
Non-credit impairment losses on available for sale securities
Net change in non-credit impairment losses on securities	301	(31)	242	(452)
Less reclassification adjustment for accretion of credit impairment losses included in net income	0	(20)	(286)	(104)
Total	301	(51)	(44)	(556)
Unrealized gains and losses on derivatives (cash flow hedges)
Net (losses) gains on derivatives arising during the period	(2,122)	1,131	(8,674)	(4,128)
Less reclassification adjustment for net losses included in net income	2,107	991	3,848	1,942
Total	(15)	2,122	(4,826)	(2,186)
Defined benefit pension plan
Amortization of net loss	43	121	86	240
Total other comprehensive (loss) income	(304)	(3,598)	2,696	(5,765)
Total comprehensive income	$ 38,723	$ 28,393	$ 77,910	$ 56,567