Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation - Expense and Related Tax Effects (Details)

v3.8.0.1
Stock-Based Compensation - Expense and Related Tax Effects (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]      
Stock-based compensation expense $ 2.3 $ 6.7 $ 6.1
Income tax benefit $ 0.8 $ 2.5 $ 2.1