Business Combinations - Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Summary of unaudited consolidated pro forma results of operations
Revenues	$ 5,254.1	$ 5,171.3	$ 10,123.5	$ 9,931.5
Income from continuing operations	94.7	95.3	174.1	173.0
Net income	$ 93.5	$ 95.2	$ 172.9	$ 172.0
Income from continuing operations per diluted common share (in dollars per share)	$ 1.11	$ 1.06	$ 2.01	$ 1.92
Net income per diluted common share (in dollars per share)	$ 1.10	$ 1.05	$ 1.99	$ 1.91

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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)-(3)
-URI http://asc.fasb.org/extlink&oid=56956515&loc=d3e1392-128463

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The pro forma income from continuing operations before changes in accounting and extraordinary items, net of tax effect, per diluted share of common stock for a period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma income from continuing operations before changes in accounting and extraordinary items, net of tax effect, for the period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

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