Balance Sheet Offsetting (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Offsetting Liabilities
Gross Amounts Recognized	$ 194,649	$ 224,212
Gross Amounts Offset	0	0
Net Amounts Presented	194,649	224,212
Gross Amounts Not Offset, Financial Instruments	(159)	(5,376)
Gross Amounts Not Offset, Cash Collateral	(148,564)	(208,141)
Net Amount	45,926	10,695
Repurchase agreements
Offsetting Repurchase Agreement Liabilities
Gross Amounts Recognized	150,000	200,000
Gross Amounts Offset	0	0
Net Amounts Presented	150,000	200,000
Gross Amounts Not Offset, Financial Instruments	0	0
Gross Amounts Not Offset, Cash Collateral	(150,000)	(200,000)
Net Amount	0	0
Interest rate swaps
Offsetting Assets
Gross Amounts Recognized	28,205	26,346
Gross Amounts Offset	0	0
Net Amounts Presented	28,205	26,346
Gross Amounts Not Offset, Financial Instruments	(159)	(5,376)
Gross Amounts Not Offset, Cash Collateral	0	0
Net Amount	28,046	20,970
Offsetting Liabilities
Gross Amounts Recognized	44,649	24,212
Gross Amounts Offset	0	0
Net Amounts Presented	44,649	24,212
Gross Amounts Not Offset, Financial Instruments	(159)	(5,376)
Gross Amounts Not Offset, Cash Collateral	1,436	(8,141)
Net Amount	$ 45,926	$ 10,695