Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Allowance for doubtful accounts receivable current	$ 1.8	$ 1.5
Common stock, shares authorized	100,000,000
Common stock, shares issued	18,479,684
Common stock, shares outstanding	18,479,684
Common Class A [Member]
Common stock, par value		$ 1
Common stock, shares authorized	0	75,000,000
Common stock, shares issued	0	13,401,938
Common stock, shares outstanding	0	13,401,938
Common Class B [Member]
Common stock, par value		$ 1
Common stock, shares authorized	0	25,000,000
Common stock, shares issued	0	5,077,746
Common stock, shares outstanding	0	5,077,746