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Commitments and Contingencies, Contractual Commitments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Agency Business Commitments
Cash collateral	$ 210,875	$ 180,606	$ 139,398	$ 29,315
Debt Obligations
2020	1,629,115
2021	495,601
2022	1,479,600
2023	496,049
2024	215,154
Thereafter	363,344
Total	4,678,863
Minimum Annual Operating Lease Payments
2020	5,301
2021	3,044
2022	2,775
2023	2,052
2024	1,459
Thereafter	3,304
Total	17,935
Total
2020	1,634,416
2021	498,645
2022	1,482,375
2023	498,101
2024	216,613
Thereafter	366,648
Total	$ 4,696,798
Operating Lease, Weighted average remaining lease term (in years)	5 years 2 months 12 days
Operating Lease, Weighted average discount rate (as a percent)	4.70%
Operating lease expense	$ 6,100	$ 5,400	$ 4,700
Unfunded CLO Commitments
Unfunded commitments related to structured loans and investments	163,800
Fannie Mae
Agency Business Commitments
Minimum liquid assets to be maintained to meet operational liquidity requirements	$ 14,400
Period of funding for collateral requirement	48 months
Forward Contracts
Agency Business Commitments
Period of contractual commitment	60 days
Minimum
Total
Remaining lease term	8 months 12 days
Maximum
Total
Remaining lease term	7 years 2 months 12 days
Restricted liquidity arrangement - loans sold under the Fannie Mae DUS program \| Fannie Mae
Agency Business Commitments
Letter of credit assigned	$ 45,000
Cash collateral	1,900
Reserve required to fund additional restricted liquidity over the next 48 months	$ 36,300
Period of additional funding for collateral requirement	48 months
Cash collateral arrangement - purchase and loss obligations under Freddie Mac's SBL Program
Agency Business Commitments
Cash collateral per securitization	$ 5,000
Outstanding letters of credit	$ 5,000