Funding Sources Network LeaseCo (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Apr. 30, 2016	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Sale Leaseback Transaction, Net Book Value		$ 1,200	$ 447	$ 1,300
Sale Leaseback Transaction, Net Proceeds, Financing Activities		$ 600
Network Sale-Leaseback [Member]
Sale Leaseback Transaction, Net Book Value	$ 3,000		2,500
Sale Leaseback Transaction, Net Proceeds, Financing Activities	$ 2,200
Long-term Debt and Capital Lease Obligations, Repayments of Principal in Next Twelve Months			300
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Two			$ 1,900