Variable Interest Entities - Revenue and Net Income from Entities (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Variable Interest Entity [Line Items]
Total revenue	$ 2,292	$ 1,515	$ 4,367	$ 2,869
Net income	189	186	353	336
Other VIE [Member]
Variable Interest Entity [Line Items]
Total revenue	61	40	108	81
Net income	$ 9	$ 8	$ 16	$ 19