Repurchase Agreements Counterparty Information (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($) Agreements
Repurchase Agreement Counterparty [Line Items]
Borrowings outstanding with counterparty	$ 303,564
Weighted Average Rate	2.93%
Equity at Risk	$ 47,192
Line of Credit Facility, Amount Outstanding	228,992
Line of Credit Facility, Maximum Borrowing Capacity	$ 400,000
Line of Credit Facility, Expiration Date	May 12, 2019
Line of Credit Facility, Interest Rate at Period End	3.10%
Number of Counterparties with Borrowings Outstanding | Agreements	17
Available Repurchase Agreement Counterparties | Agreements	35