Expenses - Schedule of Expenses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Other Expenses [Abstract]
Insurance	$ 28	$ 21	$ 58	$ 44
Regulatory fees and assessments	18	18	45	38
Securities processing	9	6	16	10
Litigation	(17)	0	(17)	0
Other	94	93	181	158
Total other expenses	$ 132	$ 138	$ 283	$ 250