Other Assets - Schedule of Others Assets (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Loans subject to repurchase from Ginnie Mae	$ 629	$ 266
Trade receivables and accrued revenues	142	145
Right-of-use assets	126	0
Goodwill	120	23
Intangible assets	93	117
Other	339	244
Total other assets	$ 1,449	$ 795