Mortgage Servicing Rights and Related Liabilities - UPB related to owned MSRs (Details) - Mortgage Servicing Right [Member] - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Owned Service Loans [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	$ 303,091	$ 271,189
Fair Value	3,666	2,703
Agency
Owned Service Loans [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	266,588	227,136
Fair Value	3,329	2,305
Non-agency
Owned Service Loans [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	36,503	44,053
Fair Value	$ 337	$ 398

Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122492-111745

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=125521744&loc=d3e122625-111746

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

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