Derivative Financial Instruments Fair Value Gains and Losses on Derivative Financial Instruments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative [Line Items]
Net fair value gains on derivative financial instruments	$ (8,378)	$ 623
Interest rate lock with customers [Member]
Derivative [Line Items]
Net fair value gains on derivative financial instruments	129	845
Forward Commitments [Member]
Derivative [Line Items]
Net fair value gains on derivative financial instruments	226	(2,379)
Interest Rate Swap with Customer [Member]
Derivative [Line Items]
Net fair value gains on derivative financial instruments	(42,642)	(815)
Interest Rate Swap with Counterparty [Member]
Derivative [Line Items]
Net fair value gains on derivative financial instruments	33,814	3,001
Foreign Exchange Contracts With Customer [Member]
Derivative [Line Items]
Net fair value gains on derivative financial instruments	7	8
Foreign Exchange Contracts With Correspondent Banks [Member]
Derivative [Line Items]
Net fair value gains on derivative financial instruments	88	(37)
Centrally Cleared Interest Rate Swap with Counterparty [Member]
Derivative [Line Items]
Net fair value gains on derivative financial instruments	$ 8,900	$ 2,200