Fair Value Measurements - Level 3 Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Excess spread financing
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	$ 1,184
Total gains or losses included in earnings	(69)
Payments received from borrowers	0
Purchases	0
Issuances	245
Sales	0
Repayments	(1)
Settlements	(50)
Balance - end of period	1,309
Mortgage servicing rights financing
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	32
Total gains or losses included in earnings	2
Payments received from borrowers	0
Purchases	0
Issuances	0
Sales	0
Repayments	0
Settlements	0
Balance - end of period	34
Mortgage servicing rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	3,665
Total gains or losses included in earnings	(399)
Payments received from borrowers	0
Purchases	409
Issuances	66
Sales	(260)
Repayments	0
Settlements	0
Balance - end of period	3,481
Mortgage loans held for investment
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	119
Total gains or losses included in earnings	1
Payments received from borrowers	(2)
Purchases	0
Issuances	0
Sales	0
Repayments	0
Settlements	0
Balance - end of period	$ 118
Predecessor | Excess spread financing
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period		$ 996
Total gains or losses included in earnings		50
Purchases		0
Issuances		0
Sales		0
Repayments		0
Settlements		(45)
Balance - end of period		1,001
Predecessor | Mortgage servicing rights financing
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period		10
Total gains or losses included in earnings		24
Purchases		0
Issuances		0
Sales		0
Repayments		0
Settlements		0
Balance - end of period		34
Predecessor | Mortgage servicing rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period		2,937
Total gains or losses included in earnings		170
Purchases		19
Issuances		68
Sales		0
Repayments		0
Settlements		0
Balance - end of period		$ 3,194