Financing Agreements - Financing Agreements, at Fair Values Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Financing Agreements [Line Items]
Financial instruments	$ 6,378,782	$ 4,336,976
Financing Agreement
Financing Agreements [Line Items]
Cash collateral pledged	10,200	$ 7,200
Non-mark-to-market financing secured by residential whole loans
Financing Agreements [Line Items]
Financial instruments	$ 559,800
Minimum \| Non-mark-to-market financing secured by residential whole loans
Financing Agreements [Line Items]
Facility maturity period	5 months
Extension term	16 months
Maximum \| Non-mark-to-market financing secured by residential whole loans
Financing Agreements [Line Items]
Facility maturity period	45 months
Extension term	42 months

Amount of right to receive cash collateral under master netting arrangements that have not been offset against securities sold under agreement to repurchase.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226016-175313

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226038-175313

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (d)(2)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Name:	us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseCollateralRightToReclaimCash
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant