Fair Value Measurements - Fair Value by Balance Sheet Line Item (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Financial assets
Loans subject to repurchase from Ginnie Mae	$ 966	$ 1,865
Financial liabilities
Unsecured senior notes, net	3,151	2,673
Advance, warehouse and MSR facilities, net	4,302	2,885
Fair Value, Nonrecurring
Financial assets
Cash and cash equivalents	571	527
Restricted cash	169	175
Advances and other receivables, net	996	1,019
Loans subject to repurchase from Ginnie Mae	966	1,865
Financial liabilities
Unsecured senior notes, net	3,151	2,673
Advance, warehouse and MSR facilities, net	4,302	2,885
Liability for loans subject to repurchase from Ginnie Mae	966	1,865
Fair Value, Nonrecurring | Level 1
Financial assets
Cash and cash equivalents	571	527
Restricted cash	169	175
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
Loans subject to repurchase from Ginnie Mae	966	1,865
Financial liabilities
Unsecured senior notes, net	3,056	2,209
Advance, warehouse and MSR facilities, net	4,318	2,896
Liability for loans subject to repurchase from Ginnie Mae	966	1,865
Fair Value, Nonrecurring | Level 3
Financial assets
Cash and cash equivalents	0	0
Restricted cash	0	0
Advances and other receivables, net	996	1,019
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