CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 4.3	$ 3.7
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	66,287,054	65,778,891
Common stock, shares outstanding (n shares)	49,777,570	49,431,178
Non-vesting restricted shares (in shares)	913,675	725,252
Treasury shares (in shares)	16,509,484	16,347,713