Fair Value Measurements - Fair Value by Balance Sheet Line Item (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024
Financial assets
Restricted cash	$ 166	$ 220	$ 157
Loans subject to repurchase from Ginnie Mae	1,115	1,176
Financial liabilities
Unsecured senior notes, net	4,896	4,891
Advance, warehouse and MSR facilities, net	6,313	6,495
Nonrecurring Fair Value Measurements
Financial assets
Cash and cash equivalents	784	753
Restricted cash	166	220
Advances and other receivables, net	1,061	1,345
Loans subject to repurchase from Ginnie Mae	1,115	1,176
Financial liabilities
Unsecured senior notes, net	4,896	4,891
Advance, warehouse and MSR facilities, net	6,313	6,495
Liability for loans subject to repurchase from Ginnie Mae	1,115	1,176
Nonrecurring Fair Value Measurements | Level 1
Financial assets
Cash and cash equivalents	784	753
Restricted cash	166	220
Advances and other receivables, net	0	0
Loans subject to repurchase from Ginnie Mae	0	0
Financial liabilities
Unsecured senior notes, net	0	0
Advance, warehouse and MSR facilities, net	0	0
Liability for loans subject to repurchase from Ginnie Mae	0	0
Nonrecurring Fair Value Measurements | Level 2
Financial assets
Cash and cash equivalents	0	0
Restricted cash	0	0
Advances and other receivables, net	0	0
Loans subject to repurchase from Ginnie Mae	1,115	1,176
Financial liabilities
Unsecured senior notes, net	4,980	4,862
Advance, warehouse and MSR facilities, net	6,329	6,515
Liability for loans subject to repurchase from Ginnie Mae	1,115	1,176
Nonrecurring Fair Value Measurements | Level 3
Financial assets
Cash and cash equivalents	0	0
Restricted cash	0	0
Advances and other receivables, net	1,061	1,345
Loans subject to repurchase from Ginnie Mae	0	0
Financial liabilities
Unsecured senior notes, net	0	0
Advance, warehouse and MSR facilities, net	0	0
Liability for loans subject to repurchase from Ginnie Mae	$ 0	$ 0