Other Financial Information (Details) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Other Current Assets
Prepaid expenses	$ 273		$ 260
Materials, supplies and inventory	136		132
Assets held for sale	9		14
Deferred activation and installation charges	105		103
Other	71		71
Total other current assets	594		580
Impairment of long-lived assets	(9)	$ (32)
Other Current Liabilities
Accrued rent	29		34
Legal contingencies	24		27
Other	215		149
Total other current liabilities	268		210
Accounts payable	1,087		1,226
Current Liabilities
Book overdraft balance	55		80
Capital expenditures incurred but not yet paid	130		$ 185
Building
Other Current Assets
Impairment of long-lived assets	$ (9)