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New Accounting Pronouncements (Narrative) (Details) - ASU No. 2016-09 [Member] $ in Millions | 6 Months Ended
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Jun. 30, 2017 USD ($)
Reclassification from Operating Activities to Financing Activities [Member] |
New Accounting Pronouncements Or Change In Accounting Principle [Line Items] |
Shares withheld from employee awards for tax withholding purposes | $ 38.1
Incentive Stock Award Plans [Member] |
New Accounting Pronouncements Or Change In Accounting Principle [Line Items] |
Provision for income tax expense (benefit) | $ (17.1)

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