Equity Method Investments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity Method Investments [Abstract]
Equity interest in the net income of equity method investments	$ 3.5	$ 5.4	$ 8.4
Equity interest in the net assets of equity method investments	$ 40.7	$ 38.6