Fair Value Measurements - Fair Value by Balance Sheet Line Item (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Financial assets
Loans subject to repurchase from Ginnie Mae	$ 1,865	$ 1,496
Financial liabilities
Unsecured senior notes, net	2,673	2,670
Advance and warehouse facilities, net	2,885	4,997
Fair Value, Nonrecurring
Financial assets
Cash and cash equivalents	527	895
Restricted cash	175	146
Advances and other receivables, net	1,019	1,228
Loans subject to repurchase from Ginnie Mae	1,865	1,496
Financial liabilities
Unsecured senior notes, net	2,673	2,670
Advance and warehouse facilities, net	2,885	4,997
Liability for loans subject to repurchase from Ginnie Mae	1,865	1,496
Fair Value, Nonrecurring | Level 1
Financial assets
Cash and cash equivalents	527	895
Restricted cash	175	146
Advances and other receivables, net	0	0
Loans subject to repurchase from Ginnie Mae	0	0
Financial liabilities
Unsecured senior notes, net	0	2,737
Advance and warehouse 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	1,865	1,496
Financial liabilities
Unsecured senior notes, net	2,209	0
Advance and warehouse facilities, net	2,896	5,009
Liability for loans subject to repurchase from Ginnie Mae	1,865	1,496
Fair Value, Nonrecurring | Level 3
Financial assets
Cash and cash equivalents	0	0
Restricted cash	0	0
Advances and other receivables, net	1,019	1,228
Loans subject to repurchase from Ginnie Mae	0	0
Financial liabilities
Unsecured senior notes, net	0	0
Advance and warehouse facilities, net	0	0
Liability for loans subject to repurchase from Ginnie Mae	$ 0	$ 0