Net Earnings Per Share (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended			6 Months Ended	9 Months Ended
	Aug. 31, 2011	Sep. 30, 2012	Jun. 30, 2012	Sep. 30, 2011	Dec. 31, 2011	Sep. 30, 2012	Sep. 30, 2011
Net Earnings Per Share
Net earnings attributable to common stockholders		$ 403,300,000		$ 330,900,000		$ 1,378,000,000	$ 1,100,300,000
Basic earnings per common share:
Weighted average common shares outstanding		62.8		69.4		64.2	70.7
Net earnings attributable to common stockholders basic (in dollars per share)		$ 6.43		$ 4.77		$ 21.47	$ 15.55
Diluted earnings per common share:
Weighted average common shares outstanding		62.8		69.4		64.2	70.7
Dilutive common share-stock options		0.7		0.5		0.8	0.7
Diluted weighted average shares outstanding		63.5		69.9		65.0	71.4
Net earnings attributable to common stockholders diluted (in dollars per share)		$ 6.35		$ 4.73		$ 21.19	$ 15.41
Share repurchase authorized	1,500,000,000	3,000,000,000		1,500,000,000
Number of shares repurchased			3.1		6.5
Amount of shares repurchased			$ 500,000,000		$ 1,000,000,000