Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Accounts receivable - trade, allowance for doubtful accounts	$ 1.2	$ 1.1
Accumulated depreciation and amortization	$ 1,079.2
Accumulated depreciation and amortization		$ 974.2
Preferred stock par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock shares authorized (in shares)	20,000,000	20,000,000
Preferred stock shares outstanding (in shares)	0	0
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)	46,767,164	46,767,164
Treasury stock (in shares)	16,307,048	14,505,681