Recent Accounting Developments (Narrative) (Details) $ in Millions	6 Months Ended
Jun. 30, 2017 USD ($)
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Excess tax benefits within income tax expense from ASU 2016-09 adoption	$ 3.9

Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount

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