Business Combinations (Details 3) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Summary of unaudited consolidated pro forma results of operations
Revenues	$ 3,407	$ 3,072	$ 10,075	$ 9,011
Income from continuing operations	42	58	142	138
Net income	$ 41	$ 57	$ 137	$ 135
Income from continuing operations per diluted common share (in dollars per share)	$ 0.46	$ 0.63	$ 1.56	$ 1.49
Net income per diluted common share (in dollars per share)	$ 0.45	$ 0.62	$ 1.52	$ 1.46

The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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-Name Accounting Standards Codification

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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