Derivative Financial Instruments Offsetting Derivative Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Offsetting Assets [Line Items]
Derivative asset, fair value	$ 48,003	$ 41,636
Derivative, Collateral, Obligation to Return Securities	14,443	15,358
Derivative, Collateral, Obligation to Return Cash	0	0
Net Amount	33,560	26,278
Derivative liability, gross liability	41,625	41,842
Derivative liability, Collateral, Right to Reclaim Securities	(14,443)	(15,358)
Derivative liability, Collateral, Right to Reclaim Cash	(15,520)	(4,216)
Derivative liability, Net Amount	11,662	22,268
Interest Rate Swap [Member]
Offsetting Assets [Line Items]
Derivative asset, fair value	47,710	41,395
Derivative, Collateral, Obligation to Return Securities	14,163	15,117
Derivative, Collateral, Obligation to Return Cash	0	0
Net Amount	33,547	26,278
Derivative liability, gross liability	41,345	41,395
Derivative liability, Collateral, Right to Reclaim Securities	(14,163)	(15,117)
Derivative liability, Collateral, Right to Reclaim Cash	(15,520)	(4,010)
Derivative liability, Net Amount	11,662	22,268
Foreign Exchange Contract [Member]
Offsetting Assets [Line Items]
Derivative asset, fair value	293	241
Derivative, Collateral, Obligation to Return Securities	280	241
Derivative, Collateral, Obligation to Return Cash	0	0
Net Amount	13	0
Derivative liability, gross liability	280	447
Derivative liability, Collateral, Right to Reclaim Securities	(280)	(241)
Derivative liability, Collateral, Right to Reclaim Cash	0	(206)
Derivative liability, Net Amount	$ 0	$ 0