Basis of Presentation and Summary of Significant Accounting Policies (Details 2) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Change in accounting estimates
Depreciation									$ 2,836	$ 2,958	$ 2,952
Net income (loss)	$ 338	$ 205	$ 143	$ 192	$ 188	$ 188	$ 193	$ 203	878	772	$ (239)
Service life | Switch, circuit and cable network equipment
Change in accounting estimates
Depreciation										78
Net income (loss)										$ 48
Earnings per share, basic and diluted										$ 0.08
Service life | Network assets, future abandonment
Change in accounting estimates
Depreciation									48	$ 12
Net income (loss)									$ 32	$ 7
Earnings per share, basic and diluted									$ 0.06	$ 0.01