Derivative Financial Instruments Offsetting Derivative Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Offsetting Assets [Line Items]
Derivative asset, fair value	$ 56,717	$ 43,630
Derivative, Collateral, Obligation to Return Securities	6,212	17,028
Derivative, Collateral, Obligation to Return Cash	(44,080)	0
Net Amount	6,425	26,602
Derivative liability, gross liability	62,438	38,997
Derivative liability, Collateral, Right to Reclaim Securities	(6,212)	(17,028)
Derivative liability, Collateral, Right to Reclaim Cash	(13,177)	(6,588)
Derivative liability, Net Amount	43,049	15,381
Interest Rate Swap [Member]
Offsetting Assets [Line Items]
Derivative asset, fair value	56,421	43,446
Derivative, Collateral, Obligation to Return Securities	5,916	16,844
Derivative, Collateral, Obligation to Return Cash	(44,080)	0
Net Amount	6,425	26,602
Derivative liability, gross liability	62,109	38,742
Derivative liability, Collateral, Right to Reclaim Securities	(5,916)	(16,844)
Derivative liability, Collateral, Right to Reclaim Cash	(13,177)	(6,588)
Derivative liability, Net Amount	43,016	15,310
Foreign Exchange Contract [Member]
Offsetting Assets [Line Items]
Derivative asset, fair value	296	184
Derivative, Collateral, Obligation to Return Securities	296	184
Derivative, Collateral, Obligation to Return Cash	0	0
Net Amount	0	0
Derivative liability, gross liability	329	255
Derivative liability, Collateral, Right to Reclaim Securities	(296)	(184)
Derivative liability, Collateral, Right to Reclaim Cash	0	0
Derivative liability, Net Amount	$ 33	$ 71