Consolidated Balance Sheet (Parenthetical) - USD ($) shares in Millions, $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Accounts receivable, related party receivables	$ 6.7	$ 19.7
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	10.0	10.0
Preferred stock, shares issued	0.0	0.0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	400.0	400.0
Common stock, shares issued	64.4	82.0