Other Assets - Schedule of Others Assets (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Loans subject to repurchase from Ginnie Mae	$ 723	$ 266
Accrued revenues	136	145
Right-of-use assets	139	0
Intangible assets	105	117
Goodwill	120	23
Other	306	244
Total other assets	$ 1,529	$ 795