Derivative Financial Instruments Offsetting Derivative Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Offsetting Assets [Line Items]
Derivative asset, fair value	$ 66,020	$ 43,630
Derivative, Collateral, Obligation to Return Securities	4,854	17,028
Derivative, Collateral, Obligation to Return Cash	(56,630)	0
Net Amount	4,536	26,602
Derivative liability, gross liability	75,146	38,997
Derivative liability, Collateral, Right to Reclaim Securities	(4,854)	(17,028)
Derivative liability, Collateral, Right to Reclaim Cash	(13,628)	(6,588)
Derivative liability, Net Amount	56,664	15,381
Interest Rate Swap [Member]
Offsetting Assets [Line Items]
Derivative asset, fair value	65,695	43,446
Derivative, Collateral, Obligation to Return Securities	4,662	16,844
Derivative, Collateral, Obligation to Return Cash	(56,630)	0
Net Amount	4,403	26,602
Derivative liability, gross liability	74,954	38,742
Derivative liability, Collateral, Right to Reclaim Securities	(4,662)	(16,844)
Derivative liability, Collateral, Right to Reclaim Cash	(13,628)	(6,588)
Derivative liability, Net Amount	56,664	15,310
Foreign Exchange Contract [Member]
Offsetting Assets [Line Items]
Derivative asset, fair value	325	184
Derivative, Collateral, Obligation to Return Securities	192	184
Derivative, Collateral, Obligation to Return Cash	0	0
Net Amount	133	0
Derivative liability, gross liability	192	255
Derivative liability, Collateral, Right to Reclaim Securities	(192)	(184)
Derivative liability, Collateral, Right to Reclaim Cash	0	0
Derivative liability, Net Amount	$ 0	$ 71