Fair Value Measurements - Fair Value by Balance Sheet Line Item (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Financial liabilities
Unsecured senior notes, net	$ 4,891	$ 3,151
Advance, warehouse and MSR facilities, net	6,495	4,302
Fair Value, Nonrecurring
Financial assets
Cash and cash equivalents	753	571
Restricted cash	220	169
Advances and other receivables, net	1,345	996
Loans subject to repurchase from Ginnie Mae	1,176	966
Financial liabilities
Unsecured senior notes, net	4,891	3,151
Advance, warehouse and MSR facilities, net	6,495	4,302
Liability for loans subject to repurchase from Ginnie Mae	1,176	966
Fair Value, Nonrecurring | Level 1
Financial assets
Cash and cash equivalents	753	571
Restricted cash	220	169
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
Fair Value, Nonrecurring | 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	1,176	966
Financial liabilities
Unsecured senior notes, net	4,862	3,056
Advance, warehouse and MSR facilities, net	6,515	4,318
Liability for loans subject to repurchase from Ginnie Mae	1,176	966
Fair Value, Nonrecurring | Level 3
Financial assets
Cash and cash equivalents	0	0
Restricted cash	0	0
Advances and other receivables, net	1,345	996
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