Equity (Details) (USD $) In Millions, except Share data, unless otherwise specified	6 Months Ended	12 Months Ended									12 Months Ended							12 Months Ended					12 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010		Jun. 30, 2012	Dec. 07, 2011 agreements	Jun. 29, 2011	Dec. 31, 2012 2011 Repurchase Program [Member]		Dec. 31, 2011 2011 Repurchase Program [Member]		Dec. 31, 2010 2011 Repurchase Program [Member]		Jun. 29, 2011 2011 Repurchase Program [Member]	Dec. 31, 2012 2007 Repurchase Program [Member]	Dec. 31, 2011 2007 Repurchase Program [Member]	Dec. 31, 2010 2007 Repurchase Program [Member]	Dec. 31, 2012 First ASR Agreement [Member]	Dec. 31, 2012 Second ASR Agreement [Member]	Dec. 31, 2012 Uncollared ASR Agreement [Member]	Dec. 12, 2011 Uncollared ASR Agreement [Member]	Dec. 31, 2012 Capped ASR Agreement [Member]	Dec. 31, 2012 Subsequent Event [Member]
Dividend history
Quarterly dividend rate (in usd per share)		$ 0.255		$ 0.250		$ 0.235																				$ 0.28
Annualized dividend rate (in usd per share)		$ 1.02		$ 1.0		$ 0.94
Special dividend (in usd per share)		$ 2.50		$ 0		$ 0
Dividends paid		$ 984	[1]	$ 296	[1]	$ 292	[1]
Share repurchases
Total number of shares purchased (shares)											6,800,000	[2]	26,300,000	[2]	0	[2]		0	8,400,000	8,700,000
Average price paid per share (in usd per share)		$ 50.35	[1]	$ 40.48	[1]	$ 29.37	[1]
Total cash utilized		295		1,500		256
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Opening redeemable noncontrolling interest	810	810		0				792
Net income attributable to noncontrolling interest	34
Distributions to noncontrolling interest	(33)	(223)		(7)		(17)
Redemption value adjustment	17
Ending redeemable noncontrolling interest	810	810		0				792
Equity (Textual) [Abstract]
Preferred stock authorized (shares)	2,000,000	2,000,000
Par value of Preferred stock (in usd per share)	$ 1	$ 1
Quarterly dividend rate (in usd per share)		$ 0.255		$ 0.250		$ 0.235																				$ 0.28
Stock repurchase program number of shares authorized to be repurchased (shares)				45,000,000													50,000,000
Maximum number of shares authorized for repurchase under stock repurchase plan as percentage of outstanding common stock										17.00%
Remaining shares available under repurchase program											16,900,000							0
Accelerated Share Repurchase Program, Number of Agreements Entered									2
Repurchase of additional shares				500
Repurchase of shares at a per share price																					250	250		250	250
Percentage of VWAP of common stock																						110.00%
Shares received on initial delivery																							5,000,000		5,000,000
Percentage of shares received on initial delivery																							20.00%
Shares hold back on initial delivery																							$ 50
Accelerated Share Repurchases Additional Shares Acquired																							800,000		100,000
Accelerated Share Repurchases Shares Acquired																							6,000,000		5,000,000
Interest In Joint Venture Minimum Percentage		20.00%
Business Acquisition, Agreement Terms, Change of Control, Put Option for Minority Interest Ownership, Effective Period		15 days

[1] Average price paid per share information does not include the accelerated share repurchase transaction as discussed in more detail below.

[2] 2012 includes shares received at the conclusion of the uncollared Accelerated Share Repurchase Agreement described in more detail below.