Basis of Presentation and Significant Accounting Policies (Details) - USD ($) shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accounting Policies [Abstract]
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	$ 2.9		$ 3.7
Tax paid for net share exercises and issuance of vested restricted stock units				$ 1.6
Payments Related to Tax Withholding for Share-based Compensation				$ 5.6
Weighted Average Number Diluted Shares Outstanding Adjustment		179	195