Repurchase Agreements - Borrowings Under Financing Arrangements and Associated Assets Pledged as Collateral (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2021	Dec. 31, 2020
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Carrying Value of Loans Pledged	$ 3,206,282	$ 3,049,166
Residential loans
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Carrying Value of Loans Pledged	1,316,707	1,090,930
Residential loans
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Maximum Aggregate Uncommitted Principal Amount	1,456,691	1,301,389
Outstanding Repurchase Agreements	538,632	407,213
Net Deferred Finance Costs	(1,583)	(1,682)
Carrying Value of Loans Pledged	$ 742,429	$ 575,380
Weighted Average Rate	2.92%	2.92%
Weighted Average Months to Maturity	10 years 7 days	11 years 11 months 1 day
Residential loans \| Repurchase agreements
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Carrying Value of Repurchase Agreements	$ 537,049	$ 405,531
Residential loans \| Repurchase Agreement, Non Mark-to Market
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Outstanding Repurchase Agreements	$ 208,700	$ 49,800
Weighted Average Rate	3.15%	4.00%
Weighted Average Months to Maturity	11 years 10 days	8 years 9 months 18 days

Assets Sold under Agreements to Repurchase, Deferred Finance Costs, Net

No definition available.

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- Definition

The total amount of repossession that is available under the repurchase agreement.

+ References

No definition available.

+ Details

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- Definition

Carrying amount of assets sold under agreements to repurchase when the carrying amount (or market value, if higher than the carrying amount) of securities or other assets sold under repurchase agreements exceeds 10 percent of total assets.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(m)(1)(i)(A)(i))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

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- Definition

Interest rate on the amount to be repaid to the counterparty to the repurchase agreement when the carrying amount (or market value, if higher than the carrying amount) of securities or other assets sold under the repurchase agreement exceeds 10 percent of total assets.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(m)(1)(i)(A)(ii))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

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- Definition

Amount to be repaid to the counterparty to the repurchase agreement when the carrying amount (or market value, if higher than the carrying amount) of securities or other assets sold under the repurchase agreement exceeds 10 percent of total assets.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(m)(1)(i)(A)(ii))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

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- Definition

Amount of investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column G))
-URI http://asc.fasb.org/extlink&oid=120402547&loc=d3e617274-123014

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- Definition

Weighted average maturity (weighted by amount of the agreement) of repurchase agreements with the counterparty, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(m)(1)(i)(B)(iii))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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