Other Financial Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Other Current Assets
Prepaid expenses	$ 293		$ 260
Materials, supplies and inventory	137		132
Assets held for sale	18		14
Deferred activation and installation charges	104		103
Other	70		71
Total other current assets	622		580
Impairment of long-lived assets	8	0
Selected Current Liabilities
Accounts payable	1,068		1,226
Other Current Liabilities
Accrued rent	28		34
Legal reserves	43		27
Other	188		149
Total other current liabilities	259		210
Current Liabilities
Book overdraft balance	62		80
Capital expenditures incurred but not yet paid	$ 107		$ 185