Quarterly Financial Data (Unaudited) Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Effect of Fourth Quarter Events [Line Items]
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	$ 1.8	$ 1.8	$ (0.1)