Recent Accounting Pronouncements Recent Accounting Pronouncements (Narrative) (Details) - Adoption of ASU 2016-09 [Member] - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Recent Accounting Pronouncements
Change in accounting policy, description	Upon adoption of ASU 2016-09, the Company elected to change its accounting policy to account for forfeitures as they occur; this change was applied using the modified retrospective transition method with a cumulative effect adjustment
Excess tax benefit from share-based compensation	$ 23.3
Reclassification or adjustment due to the adoption of a accounting pronouncement [Member]
Recent Accounting Pronouncements
Cumulative effect adjustment to opening Retained earnings	$ (0.3)
Tax withholdings for share-based compensation		$ 0.2
Excess tax benefit from share-based compensation		$ 14.8
Effect on diluted earnings per share	$ 0.23

Amount of cumulative effect of the change in accounting principle or new accounting pronouncement on retained earnings or other components of equity or net assets in the statement of financial position as of the beginning of the earliest period presented.

Disclosure related to a new accounting pronouncement or a change in accounting principle, including the nature and reason for the change and the effect of the change on prior periods and the current period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=68064558&loc=d3e765-108305

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Retrospective Application
-URI http://asc.fasb.org/extlink&oid=6523989

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=6503790

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+ Details

- Definition

Amount of the effect of a change in accounting principle on diluted earnings per share.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6523989

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+ Details