Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable, current	$ 1.3	$ 1.1
Accumulated depreciation, properties and equipment	112.0	108.9
Accumulated depreciation, rental equipment	18.9	20.0
Accumulated amortization, intangible assets	$ 7.5	$ 5.5
Common stock, par value (usd per share)	$ 1	$ 1
Common stock, shares authorized (shares)	90,000,000	90,000,000
Common stock, shares issued (shares)	66,100,000	66,100,000
Treasury stock, shares (shares)	6,100,000	6,100,000