Consolidated Statements of Changes in Equity (USD $) In Millions, except Share data, unless otherwise specified	Total	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Non-Controlling Interest [Member]
Beginning Balance at Dec. 31, 2011	$ 7,053	$ 3,417	$ 3,750	$ (158)	$ 44
Beginning Balance (in shares) at Dec. 31, 2011		169,247,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	618		610		8
Dividends declared on common stock	(414)		(414)
Issuance of common stock (in shares)		684,000
Issuance of common stock	39	39
Contribution of common stock to pension plan (in shares)		1,335,000
Contribution of common stock to pension plan	80	80
Benefit obligations, net of tax	(2)			(2)
Net change in unrealized losses on investments, net of tax	1			1
Foreign currency translation, net of tax	1			1
Stock-based compensation, distributions to noncontrolling interests and other (in shares)		1,086,000
Stock-based compensation, distributions to noncontrolling interests and other	35	51	(2)		(14)
Ending Balance at Dec. 31, 2012	7,411	3,587	3,944	(158)	38
Ending Balance (in shares) at Dec. 31, 2012		172,352,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	668		661		7
Dividends declared on common stock	(454)		(454)
Issuance of common stock (in shares)		589,000
Issuance of common stock	39	39
Contribution of common stock to pension plan (in shares)		3,026,000
Contribution of common stock to pension plan	200	200
Benefit obligations, net of tax	22			22
Net change in unrealized losses on investments, net of tax	2			2
Foreign currency translation, net of tax	(2)			(2)
Stock-based compensation, distributions to noncontrolling interests and other (in shares)		1,120,000
Stock-based compensation, distributions to noncontrolling interests and other	68	81	(1)		(12)
Ending Balance at Dec. 31, 2013	7,954	3,907	4,150	(136)	33
Ending Balance (in shares) at Dec. 31, 2013	177,087,230	177,087,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	911		905		6
Dividends declared on common stock	(476)		(476)
Repurchase of common stock (in shares)		(713,000)
Repurchase of common stock	(52)	(52)
Benefit obligations, net of tax	(18)			(18)
Net change in unrealized losses on investments, net of tax	1			1
Foreign currency translation, net of tax	(2)			(2)
Stock-based compensation, distributions to noncontrolling interests and other (in shares)		617,000
Stock-based compensation, distributions to noncontrolling interests and other	24	49	(1)		(24)
Ending Balance at Dec. 31, 2014	$ 8,342	$ 3,904	$ 4,578	$ (155)	$ 15
Ending Balance (in shares) at Dec. 31, 2014	176,991,231	176,991,000