Borrowings (Details) $ in Thousands |
9 Months Ended | 12 Months Ended | |||||
|---|---|---|---|---|---|---|---|
|
Aug. 18, 2017
USD ($)
|
Sep. 30, 2017
USD ($)
counterparties
|
Dec. 31, 2016
USD ($)
counterparties
|
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| Borrowings [Line Items] | |||||||
| Total secured borrowings | $ 1,119,000 | $ 1,058,000 | |||||
| Number of Counterparties with Outstanding Reverse Repurchase Agreements | counterparties | 21 | 21 | |||||
| Concentration Risk, Reverse Repurchase Agreements | 15.00% | 15.00% | |||||
| Number Counterparties With Concentration Risk, Reverse Repurchase Agreements | counterparties | 1 | 0 | |||||
| Investments held with dealers as collateral | $ 1,160,000 | $ 1,150,000 | |||||
| Pledged Financial Instruments, Not Separately Reported, Securities For Repurchase Agreements Unsettled | $ 13,100 | 33,400 | |||||
| Repurchase Agreements amount at risk threshold | 10.00% | ||||||
| Other secured borrowings | $ 89,646 | $ 24,086 | |||||
| Minimum [Member] | |||||||
| Borrowings [Line Items] | |||||||
| Reverse Repurchase Agreements Maturity | 30 days | ||||||
| Reverse Repurchase Agreements Remaining Terms | 2 days | 3 days | |||||
| Reverse Repurchase Agreements Interest Rate | (1.75%) | 0.60% | |||||
| Maximum [Member] | |||||||
| Borrowings [Line Items] | |||||||
| Reverse Repurchase Agreements Maturity | 180 days | ||||||
| Reverse Repurchase Agreements Remaining Terms | 360 days | 320 days | |||||
| Reverse Repurchase Agreements Interest Rate | 4.57% | 3.76% | |||||
| Reverse Repurchase Agreements [Member] | |||||||
| Borrowings [Line Items] | |||||||
| Cash collateral posted for securities sold under agreements to repurchase | [1],[2] | $ 23,300 | $ 39,200 | ||||
| Security Owned and Pledged as Collateral, Fair Value | 1,500 | 2,700 | |||||
| Secured borrowing facility collateralized by unsecured loan portfolio [Member] | |||||||
| Borrowings [Line Items] | |||||||
| Other secured borrowings | $ 46,900 | ||||||
| Effective interest rate on borrowing | 4.84% | ||||||
| Secured borrowing facility collateralized by commercial mortgage loans and REO [Member] | |||||||
| Borrowings [Line Items] | |||||||
| Other secured borrowings | $ 42,700 | 24,100 | |||||
| Loans and REO pledged as collateral | $ 75,500 | $ 42,000 | |||||
| Effective interest rate on borrowing | 4.58% | ||||||
| Senior Notes [Member] | |||||||
| Borrowings [Line Items] | |||||||
| Effective interest rate on borrowing | 5.55% | ||||||
| Debt Instrument, Face Amount | $ 86,000 | ||||||
| Proceeds from Debt, Net of Issuance Costs | $ 84,700 | ||||||
| Debt Instrument, Interest Rate, Stated Percentage | 5.25% | ||||||
| Debt Instrument, Maturity Date | Sep. 01, 2022 | ||||||
| |||||||