Restructuring - Schedule of Restructuring Charges (Details) $ in Millions	6 Months Ended
	Jun. 30, 2016 USD ($)
Severance and Related Costs
Restructuring Reserve
Liability as of January 1, 2016	$ 52
Additional costs and expenses	8
Payments	(46)
June 30, 2016	14
Lease Restructuring
Restructuring Reserve
Liability as of January 1, 2016	415
Additional costs and expenses	0
Payments	(44)
June 30, 2016	$ 371