Stock-Based Compensation (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of Shares, Outstanding, beginning balance (in shares)	13.7
Number of Shares, Granted (in shares)	2.9
Number of Shares, Exercised (in shares)	(2.5)
Number of Shares, Forfeited or expired (in shares)	(0.2)
Number of Shares, Outstanding, ending balance (in shares)	13.9
Number of Shares, Exercisable (in shares)	7.2
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted Average Exercise Price per Share, Outstanding, beginning balance	$ 27.51
Weighted Average Exercise Price per Share, Granted	$ 31.12
Weighted Average Exercise Price per Share, Exercised	$ 25.82
Weighted Average Exercise Price per Share, Forfeited or expired	$ 28.93
Weighted Average Exercise Price per Share, Outstanding, ending balance	$ 28.53
Weighted Average Exercise Price per Share, Exercisable	$ 27.03
Weighted Average Remaining Contractual Term (years), Outstanding	4 years 8 months 12 days
Weighted Average Remaining Contractual Term (years), Exercisable	3 years 6 months
Aggregate Intrinsic Value, Exercised	$ 14.0
Aggregate Intrinsic Value, Outstanding	62.2
Aggregate Intrinsic Value, Exercisable	$ 42.8

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(c), d(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.