Business Combinations and Asset Acquisitions (Details) - USD ($)		3 Months Ended					12 Months Ended
	Jul. 31, 2023	Dec. 31, 2024	Jun. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Oct. 31, 2024	Aug. 01, 2023
Business Acquisition [Line Items]
Goodwill, Acquired During Period								$ 21,000,000
Business Combination, Bargain Purchase, Gain Recognized, Amount							$ 4,000,000	96,000,000	$ 0
Business Combination, Bargain Purchase, Gain, Statement of Income or Comprehensive Income [Extensible Enumeration]				Other income (expense), net
Flagstar Bank, N.A.
Business Acquisition [Line Items]
Asset Acquisition, Consideration Transferred		$ 1,300,000,000
Rushmore Loan Management Services, LLC [Member]
Business Acquisition [Line Items]
Asset Acquisition, Consideration Transferred						$ 34,000,000
Customer-Related Intangible Assets | Flagstar Bank, N.A.
Business Acquisition [Line Items]
Asset Acquisition, Assets Acquired, Amount										$ 101,000,000
Mortgage servicing rights | Flagstar Bank, N.A.
Business Acquisition [Line Items]
Asset Acquisition, Assets Acquired, Amount										$ 1,200,000,000
Corporate/Other(2)
Business Acquisition [Line Items]
Goodwill, Acquired During Period								16,000,000
Servicing
Business Acquisition [Line Items]
Goodwill, Acquired During Period								5,000,000
Home Point Capital Inc
Business Acquisition [Line Items]
Business Combination, Consideration Transferred					$ 658,000,000
Acquisition costs								7,000,000
Business Combination, Consideration Transferred for MSRs					335,000,000
Business Combination, Consideration Transferred for Tender Offer					323,000,000
Price per share (in dollars per share)											$ 2.33
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Senior Note											$ 500,000,000
Mortgage servicing rights acquired											$ 1,200,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other liabilities			$ 4,000,000
Business Combination, Bargain Purchase, Gain Recognized, Description				The Company believes it was able to negotiate a bargain purchase price due to seller’s operational challenges from significant market volatility, as well as the seller’s desire to exit the business in an expedited manner.
Home Point Capital Inc | Corporate/Other(2)
Business Acquisition [Line Items]
Business Combination, Bargain Purchase, Gain Recognized, Final Amount			92,000,000
Business Combination, Bargain Purchase, Gain Recognized, Amount			$ 4,000,000					96,000,000
Roosevelt [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	$ 28,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	$ 4,000,000
Goodwill, Acquired During Period					$ 21,000,000
Acquisition costs								13,000,000
Roosevelt [Member] | Corporate/Other(2)
Business Acquisition [Line Items]
Goodwill, Acquired During Period								16,000,000
Roosevelt [Member] | Servicing
Business Acquisition [Line Items]
Goodwill, Acquired During Period								$ 5,000,000