Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Allowance for doubtful accounts receivables	$ 0.6	$ 0.3
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	100,000,000	100,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Voting Common Stock
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,880,000,000	1,880,000,000
Common stock, shares issued	177,091,171	179,488,247
Common stock, shares outstanding	177,091,171	179,488,247
Non-voting Common Stock
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	20,000,000	20,000,000
Common stock, shares issued	0	0
Common stock, shares outstanding	0	0