Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 3.4	$ 3.2
Accumulated depreciation and amortization	$ 300.3	$ 284.7
Common Stock, No Par Value	$ 0	$ 0
Common Stock, Shares Authorized	200,000,000	200,000,000
Common Stock, Shares, Outstanding	42,534,228	42,547,707
Treasury Stock, Shares	10,726,166	10,633,637