Unconsolidated Affiliate Companies (Details) - Joint Ventures - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Unconsolidated Affiliate Companies
Ownership percentage	50.00%
Net investment	$ 15.5	$ 13.6
Current assets	58.6	50.0
Non-current assets	14.2	15.7
Current liabilities	41.8	37.3
Equity	31.0	28.4
Revenue	155.2	131.6	$ 99.2
Gross profit	101.7	85.0	62.1
Income from operations	32.2	26.2	16.8
Net income	$ 24.8	$ 20.1	$ 13.1