Variable Interest Entities - Revenue and Net Income from Entities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Variable Interest Entity [Line Items]
Total revenue	$ 2,499	$ 1,707	$ 6,866	$ 4,576
Net income	147	179	500	515
Other VIE [Member]
Variable Interest Entity [Line Items]
Total revenue	51	41	159	122
Net income	$ 4	$ 6	$ 20	$ 25