Offsetting Assets and Liabilities - Offsetting of Assets (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Offsetting Assets [Line Items]
Gross Amount Of Recognized Assets	$ 10,613,000	$ 10,365,000
Gross Amount Of Assets Offset In The Balance Sheet	0	0
Net Amount Of Assets Presented In The Balance Sheet	10,613,000	10,365,000
Gross Amounts Of Financial Instruments Received Not Offset In Balance Sheet	0	0
Gross Amounts Of Cash Collateral Received Not Offset In Balance Sheet	(120,000)	(63,000)
Net Amount Of Assets	10,493,000	10,302,000
Swap [Member]
Offsetting Assets [Line Items]
Gross Amount Of Recognized Assets	8,523,000	10,302,000
Gross Amount Of Assets Offset In The Balance Sheet	0	0
Net Amount Of Assets Presented In The Balance Sheet	8,523,000	10,302,000
Gross Amounts Of Financial Instruments Received Not Offset In Balance Sheet	0	0
Gross Amounts Of Cash Collateral Received Not Offset In Balance Sheet	0	0
Net Amount Of Assets	8,523,000	10,302,000
TBA securities [Member]
Offsetting Assets [Line Items]
Gross Amount Of Recognized Assets	2,090,000	63,000
Gross Amount Of Assets Offset In The Balance Sheet	0	0
Net Amount Of Assets Presented In The Balance Sheet	2,090,000	63,000
Gross Amounts Of Financial Instruments Received Not Offset In Balance Sheet	0	0
Gross Amounts Of Cash Collateral Received Not Offset In Balance Sheet	(120,000)	(63,000)
Net Amount Of Assets	$ 1,970,000	$ 0