Mortgage Servicing Rights - Additional Information (Details) - USD ($) $ in Billions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Transfers And Servicing [Abstract]
Mortgage servicing right weighted average life	5 years 1 month 6 days	4 years 10 months 24 days
Principal Amount Outstanding on Loans Securitized or Asset-backed Financing Arrangement	$ 60.8	$ 50.6

Weighted average life of securitized assets regardless of when the transfer occurred, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107314-111719

Name:	us-gaap_AssumptionForFairValueOfAssetsOrLiabilitiesThatRelateToTransferorsContinuingInvolvementWeightedAverageLife1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration