Basis of Presentation and Summary of Significant Accounting Policies (Details 2) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2015
Change in accounting estimates
Depreciation									$ 2,958		$ 2,952		$ 3,070
Amortization of intangible assets									1,470		1,589		1,710
Net income (loss)	188	188	193	203	239	(1,045)	269	298	772		(239)		777
Basic earnings per common share (in dollars per share)	$ 0.33	$ 0.33	$ 0.34	$ 0.35	$ 0.41	$ (1.76)	$ 0.45	$ 0.48	$ 1.36		$ (0.40)		$ 1.25
Diluted earnings per common share (in dollars per share)	$ 0.33	$ 0.33	$ 0.34	$ 0.35	$ 0.41	$ (1.76)	$ 0.44	$ 0.48	$ 1.36	[1]	$ (0.40)	[1]	$ 1.25	[1]
Service life | Switch, circuit and cable network equipment
Change in accounting estimates
Depreciation									78
Net income (loss)									48
Basic earnings per common share (in dollars per share)									$ 0.08
Diluted earnings per common share (in dollars per share)									$ 0.08
Service life | Network assets, future abandonment
Change in accounting estimates
Depreciation									12
Net income (loss)									7
Basic earnings per common share (in dollars per share)									$ 0.01
Diluted earnings per common share (in dollars per share)									$ 0.01
Service life | Network assets, future abandonment | Forecast
Change in accounting estimates
Depreciation															48
Intangible assets, amortization period
Change in accounting estimates
Amortization of intangible assets									23
Net income (loss)									$ 14
Basic earnings per common share (in dollars per share)									$ 0.02
Diluted earnings per common share (in dollars per share)									$ 0.02

[1] Years Ended December 31, 2014 2013 2012 (Dollars in millions, except per share amounts, shares in thousands)Income (Loss) (Numerator): Net income (loss)$772 (239) 777Earnings applicable to non-vested restricted stock— — (1)Net income (loss) applicable to common stock for computing basic earnings (loss) per common share772 (239) 776Net income (loss) as adjusted for purposes of computing diluted earnings (loss) per common share$772 (239) 776Shares (Denominator): Weighted average number of shares: Outstanding during period572,748 604,404 622,139Non-vested restricted stock(4,313) (3,512) (2,796)Non-vested restricted stock units— — 862Weighted average shares outstanding for computing basic earnings (loss) per common share568,435 600,892 620,205Incremental common shares attributable to dilutive securities: Shares issuable under convertible securities10 — 12Shares issuable under incentive compensation plans1,294 — 2,068Number of shares as adjusted for purposes of computing diluted earnings (loss) per common share569,739 600,892 622,285Basic earnings (loss) per common share$1.36 (0.40) 1.25Diluted earnings (loss) per common share$1.36 (0.40) 1.25