Restructuring - Schedule of Restructuring Charges (Details) $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($)
Severance and Related Costs
Restructuring Reserve [Roll Forward]
Liability as of January 1, 2015	$ 42
Additional costs and expenses	8
Payments	(27)
Liability as of September 30, 2015	23
Lease Restructuring
Restructuring Reserve [Roll Forward]
Liability as of January 1, 2015	462
Additional costs and expenses	36
Payments	(63)
Liability as of September 30, 2015	$ 435