Restructuring (Details) $ in Millions	9 Months Ended
	Sep. 30, 2016 USD ($)
Restructuring Reserve [Roll Forward]
Balance at December 31, 2015	$ 4.7
Charges	0.2
Cash payments	(3.9)
Balance at September 30, 2016	1.0
Coal Mining
Restructuring Reserve [Roll Forward]
Balance at December 31, 2015	0.8
Charges	0.2
Cash payments	(0.9)
Balance at September 30, 2016	0.1
Corporate and Other
Restructuring Reserve [Roll Forward]
Balance at December 31, 2015	3.9
Charges	0.0
Cash payments	(3.0)
Balance at September 30, 2016	$ 0.9