Fair Value of Financial Instruments (Fair Value Hierarchy) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets:
Residential whole loans, at fair value	$ 1,216,902	$ 1,381,583
Fair Value	161,000	3,983,519
Total assets carried at fair value	1,616,901	6,522,565
Liabilities:
Securitized debt	869,482
Residential whole loans, at fair value
Assets:
Residential whole loans, at fair value	1,216,902	1,381,583
Liabilities:
Total liabilities carried at fair value	3,366,772
Non-Agency MBS
Assets:
Fair Value	56,766	2,063,529
Agency MBS
Assets:
Fair Value		1,664,582
CRT securities
Assets:
Fair Value	104,234	255,408
Term notes backed by MSR-related collateral
Assets:
Term notes backed by MSR related collateral	238,999	1,157,463
Financing agreements with non-mark-to-market collateral provisions
Liabilities:
Liabilities carried at fair value	1,159,213
Financing agreements with mark-to-market collateral provisions
Liabilities:
Liabilities carried at fair value	1,338,077
Level 1
Assets:
Total assets carried at fair value	0	0
Liabilities:
Securitized debt	0
Level 1 \| Residential whole loans, at fair value
Assets:
Residential whole loans, at fair value	0	0
Liabilities:
Total liabilities carried at fair value	0
Level 1 \| Non-Agency MBS
Assets:
Fair Value	0	0
Level 1 \| Agency MBS
Assets:
Fair Value		0
Level 1 \| CRT securities
Assets:
Fair Value	0	0
Level 1 \| Term notes backed by MSR-related collateral
Assets:
Term notes backed by MSR related collateral	0	0
Level 1 \| Financing agreements with non-mark-to-market collateral provisions
Liabilities:
Liabilities carried at fair value	0
Level 1 \| Financing agreements with mark-to-market collateral provisions
Liabilities:
Liabilities carried at fair value	0
Level 2
Assets:
Total assets carried at fair value	399,999	5,140,982
Liabilities:
Securitized debt	869,482
Level 2 \| Residential whole loans, at fair value
Assets:
Residential whole loans, at fair value	0	0
Liabilities:
Total liabilities carried at fair value	1,083,397
Level 2 \| Non-Agency MBS
Assets:
Fair Value	56,766	2,063,529
Level 2 \| Agency MBS
Assets:
Fair Value		1,664,582
Level 2 \| CRT securities
Assets:
Fair Value	104,234	255,408
Level 2 \| Term notes backed by MSR-related collateral
Assets:
Term notes backed by MSR related collateral	238,999	1,157,463
Level 2 \| Financing agreements with non-mark-to-market collateral provisions
Liabilities:
Liabilities carried at fair value	0
Level 2 \| Financing agreements with mark-to-market collateral provisions
Liabilities:
Liabilities carried at fair value	213,915
Level 3
Assets:
Total assets carried at fair value	1,216,902	1,381,583
Liabilities:
Securitized debt	0
Level 3 \| Residential whole loans, at fair value
Assets:
Residential whole loans, at fair value	1,216,902	1,381,583
Liabilities:
Total liabilities carried at fair value	2,283,375
Level 3 \| Non-Agency MBS
Assets:
Fair Value	0	0
Level 3 \| Agency MBS
Assets:
Fair Value		0
Level 3 \| CRT securities
Assets:
Fair Value	0	0
Level 3 \| Term notes backed by MSR-related collateral
Assets:
Term notes backed by MSR related collateral	0	$ 0
Level 3 \| Financing agreements with non-mark-to-market collateral provisions
Liabilities:
Liabilities carried at fair value	1,159,213
Level 3 \| Financing agreements with mark-to-market collateral provisions
Liabilities:
Liabilities carried at fair value	$ 1,124,162

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Fair value at acquisition of acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

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The fair value as of the balance sheet date of firm holdings in mortgages, mortgage backed securities (investment instruments that represent ownership of an undivided interest in a group of mortgages, where principal and interest from the individual mortgages are used to pay investors' principal and interest on the mortgage backed security) and asset-backed securities that are primarily paid from the cash flows of a discrete pool of receivables or other financial assets (such as credit-card receivables), either fixed or revolving, that by their terms convert into cash within a finite time period. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings.

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Fair value portion of other liabilities.

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