Derivative Financial Instruments Offsetting Derivative Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Offsetting Assets [Line Items]
Derivative asset, fair value	$ 138,494	$ 61,688
Derivative, Collateral, Obligation to Return Securities	2,034	13,085
Derivative, Collateral, Obligation to Return Cash	0	(23,270)
Net Amount	136,460	25,333
Derivative liability, gross liability	76,325	47,237
Derivative liability, Collateral, Right to Reclaim Securities	(2,034)	(22,916)
Derivative liability, Collateral, Right to Reclaim Cash	(74,291)	(22,786)
Derivative liability, Net Amount	0	1,535
Interest Rate Swap [Member]
Offsetting Assets [Line Items]
Derivative asset, fair value	138,275	61,401
Derivative, Collateral, Obligation to Return Securities	1,941	12,955
Derivative, Collateral, Obligation to Return Cash	0	(23,270)
Net Amount	136,334	25,176
Derivative liability, gross liability	76,232	47,107
Derivative liability, Collateral, Right to Reclaim Securities	(1,941)	(22,786)
Derivative liability, Collateral, Right to Reclaim Cash	(74,291)	(22,786)
Derivative liability, Net Amount	0	1,535
Foreign Exchange Contract [Member]
Offsetting Assets [Line Items]
Derivative asset, fair value	219	287
Derivative, Collateral, Obligation to Return Securities	93	130
Derivative, Collateral, Obligation to Return Cash	0	0
Net Amount	126	157
Derivative liability, gross liability	93	130
Derivative liability, Collateral, Right to Reclaim Securities	(93)	(130)
Derivative liability, Collateral, Right to Reclaim Cash	0	0
Derivative liability, Net Amount	$ 0	$ 0