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	$ 22,900	$ 15,394	$ 44,116	$ 30,634
Securities available for sale:
Unrealized holding gains (losses) on securities	812	(3,836)	3,875	(1,212)
Reclassification adjustment for gains realized in net income	(772)	(60)	(728)	(60)
Amortization of unrealized holding gains on securities transferred to the held to maturity category	(18)	(28)	(38)	(60)
Total securities	22	(3,924)	3,109	(1,332)
Derivative instruments:
Unrealized holding (losses) gains on derivative instruments	(428)	863	(1,694)	194
Totals derivative instruments	(428)	863	(1,694)	194
Defined benefit pension and post-retirement benefit plans:
Amortization of net actuarial loss recognized in net periodic pension cost	80	68	152	125
Total defined benefit pension and post-retirement benefit plans	80	68	152	125
Other comprehensive (loss) income, net of tax	(326)	(2,993)	1,567	(1,013)
Comprehensive income	$ 22,574	$ 12,401	$ 45,683	$ 29,621