Derivative Financial Instruments Fair Value Gains and Losses on Derivative Financial Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative [Line Items]
Net fair value (losses) gains on derivative financial instruments	$ (3,188)	$ 1,123	$ (13,513)	$ 4,768
Interest rate lock with customers [Member]
Derivative [Line Items]
Net fair value (losses) gains on derivative financial instruments	(533)	(59)	(173)	631
Forward Commitments [Member]
Derivative [Line Items]
Net fair value (losses) gains on derivative financial instruments	974	(48)	659	(2,270)
Interest Rate Swap with Customer [Member]
Derivative [Line Items]
Net fair value (losses) gains on derivative financial instruments	(14,763)	(47)	(69,780)	12,947
Interest Rate Swap with Counterparty [Member]
Derivative [Line Items]
Net fair value (losses) gains on derivative financial instruments	11,193	1,248	55,818	(6,582)
Foreign Exchange Contracts With Customer [Member]
Derivative [Line Items]
Net fair value (losses) gains on derivative financial instruments	(225)	140	(241)	(177)
Foreign Exchange Contracts With Correspondent Banks [Member]
Derivative [Line Items]
Net fair value (losses) gains on derivative financial instruments	166	(111)	204	219
Centrally Cleared Interest Rate Swap with Counterparty [Member]
Derivative [Line Items]
Net fair value (losses) gains on derivative financial instruments	$ 3,600	$ 1,200	$ 13,900	$ 6,300