Goodwill and Other Intangible Assets (Details Textual) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) employee	Jun. 30, 2015 USD ($)
Restructuring Cost and Reserve [Line Items]
Total amortization expense | $	$ 2.9	$ 0.3	$ 5.6	$ 0.7
Murray American Coal
Restructuring Cost and Reserve [Line Items]
Expected number of positions eliminated, up to | employee			4,400
Expected positions eliminated, as a percent of overall workforce			80.00%
Waiting period for layoff			60 days