Other Financial Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Prepaid Expenses and Other Current Assets [Abstract]
Prepaid expenses	$ 276		$ 238
Materials, supplies and inventory	136		144
Assets held for sale	2		8
Deferred activation and installation charges	106		105
Other	97		86
Total other current assets	617		581
Accounts Payable, Current [Abstract]
Accounts payable	1,039		968
Book overdraft balance	50		68
Capital expenditures incurred but not yet paid	87	$ 94
Other Current Liabilities
Accrued rent	28		32
Legal contingencies	41		20
Other	233		168
Total other current liabilities	$ 302		$ 220