Commitments - Schedule of Activity Related to HMBS Repurchases (Footnote) (Details) - Maximum Claim Amount $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($) loan
Long-term Purchase Commitment [Line Items]
Number of maximum claim amount repurchases loans \| loan	189
Amount of maximum claim amount repurchases \| $	$ 38.4

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.

No definition available.

Name:	us-gaap_LongTermPurchaseCommitmentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration