Derivative Financial Instruments Offsetting Derivative Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Offsetting Assets [Line Items]
Derivative asset, fair value	$ 47,229	$ 43,630
Derivative, Collateral, Obligation to Return Securities	7,504	17,028
Derivative, Collateral, Obligation to Return Cash	(34,170)	0
Net Amount	5,555	26,602
Derivative liability, gross liability	51,336	38,997
Derivative liability, Collateral, Right to Reclaim Securities	(7,504)	(17,028)
Derivative liability, Collateral, Right to Reclaim Cash	(8,806)	(6,588)
Derivative liability, Net Amount	35,026	15,381
Interest Rate Swap [Member]
Offsetting Assets [Line Items]
Derivative asset, fair value	47,047	43,446
Derivative, Collateral, Obligation to Return Securities	7,339	16,844
Derivative, Collateral, Obligation to Return Cash	(34,170)	0
Net Amount	5,538	26,602
Derivative liability, gross liability	51,171	38,742
Derivative liability, Collateral, Right to Reclaim Securities	(7,339)	(16,844)
Derivative liability, Collateral, Right to Reclaim Cash	(8,806)	(6,588)
Derivative liability, Net Amount	35,026	15,310
Foreign Exchange Contract [Member]
Offsetting Assets [Line Items]
Derivative asset, fair value	182	184
Derivative, Collateral, Obligation to Return Securities	165	184
Derivative, Collateral, Obligation to Return Cash	0	0
Net Amount	17	0
Derivative liability, gross liability	165	255
Derivative liability, Collateral, Right to Reclaim Securities	(165)	(184)
Derivative liability, Collateral, Right to Reclaim Cash	0	0
Derivative liability, Net Amount	$ 0	$ 71