Balance Sheet Offsetting (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Offsetting Liabilities
Gross Amounts Recognized	$ 187,586	$ 224,212
Gross Amounts Offset	0	0
Net Amounts Presented	187,586	224,212
Gross Amounts Not Offset, Financial Instruments	(336)	(5,376)
Gross Amounts Not Offset, Cash Collateral	(151,645)	(208,141)
Net Amount	35,605	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	29,834	26,346
Gross Amounts Offset	0	0
Net Amounts Presented	29,834	26,346
Gross Amounts Not Offset, Financial Instruments	(336)	(5,376)
Gross Amounts Not Offset, Cash Collateral	0	0
Net Amount	29,498	20,970
Offsetting Liabilities
Gross Amounts Recognized	37,586	24,212
Gross Amounts Offset	0	0
Net Amounts Presented	37,586	24,212
Gross Amounts Not Offset, Financial Instruments	(336)	(5,376)
Gross Amounts Not Offset, Cash Collateral	(1,645)	(8,141)
Net Amount	$ 35,605	$ 10,695