Derivative Financial Instruments Fair Value Gains and Losses on Derivative Financial Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative [Line Items]
Net fair value (losses) gains on derivative financial instruments	$ (1,947)	$ 3,022	$ (10,325)	$ 3,645
Interest rate lock with customers [Member]
Derivative [Line Items]
Net fair value (losses) gains on derivative financial instruments	231	(155)	360	690
Forward Commitments [Member]
Derivative [Line Items]
Net fair value (losses) gains on derivative financial instruments	(541)	157	(315)	(2,222)
Interest Rate Swap with Customer [Member]
Derivative [Line Items]
Net fair value (losses) gains on derivative financial instruments	(12,375)	13,809	(55,017)	12,994
Interest Rate Swap with Counterparty [Member]
Derivative [Line Items]
Net fair value (losses) gains on derivative financial instruments	10,811	(10,831)	44,625	(7,830)
Foreign Exchange Contracts With Customer [Member]
Derivative [Line Items]
Net fair value (losses) gains on derivative financial instruments	(23)	(325)	(16)	(317)
Foreign Exchange Contracts With Correspondent Banks [Member]
Derivative [Line Items]
Net fair value (losses) gains on derivative financial instruments	(50)	367	38	330
Centrally Cleared Interest Rate Swap with Counterparty [Member]
Derivative [Line Items]
Net fair value (losses) gains on derivative financial instruments	$ 1,600	$ 2,900	$ 10,400	$ 5,100