Derivative Financial Instruments Offsetting Derivative Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Offsetting Assets [Line Items]
Derivative asset, fair value	$ 80,075	$ 61,688
Derivative, Collateral, Obligation to Return Securities	14,524	13,085
Derivative, Collateral, Obligation to Return Cash	0	(23,270)
Net Amount	65,551	25,333
Derivative liability, gross liability	49,210	47,237
Derivative liability, Collateral, Right to Reclaim Securities	(14,524)	(22,916)
Derivative liability, Collateral, Right to Reclaim Cash	(34,672)	(22,786)
Derivative liability, Net Amount	14	1,535
Interest Rate Swap [Member]
Offsetting Assets [Line Items]
Derivative asset, fair value	79,885	61,401
Derivative, Collateral, Obligation to Return Securities	14,334	12,955
Derivative, Collateral, Obligation to Return Cash	0	(23,270)
Net Amount	65,551	25,176
Derivative liability, gross liability	49,006	47,107
Derivative liability, Collateral, Right to Reclaim Securities	(14,334)	(22,786)
Derivative liability, Collateral, Right to Reclaim Cash	(34,672)	(22,786)
Derivative liability, Net Amount	0	1,535
Foreign Exchange Contract [Member]
Offsetting Assets [Line Items]
Derivative asset, fair value	190	287
Derivative, Collateral, Obligation to Return Securities	190	130
Derivative, Collateral, Obligation to Return Cash	0	0
Net Amount	0	157
Derivative liability, gross liability	204	130
Derivative liability, Collateral, Right to Reclaim Securities	(190)	(130)
Derivative liability, Collateral, Right to Reclaim Cash	0	0
Derivative liability, Net Amount	$ 14	$ 0