Equity Method Investments - Results of Operations and Summary of Distributions (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
ADES equity earnings	$ 15,889		$ 10,155		$ 28,142	$ 23,969
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Distributions from equity method investees, return on investment					2,700	2,875
Included in investing cash flows					25,500	22,313
Tinuum Group, LLC
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Gross profit (loss)	28,683		25,027		55,096	47,083
Operating, selling, general and administrative expenses	5,491		4,327		11,498	9,801
Income (loss) from operations	23,192		20,700		43,598	37,282
Other income	(355)		(359)		(2,224)	(947)
Class B preferred return	0		(505)		(12)	(1,142)
Loss attributable to noncontrolling interest	10,244		7,926		21,019	17,287
Net income available to members	33,081		27,762		62,381	52,480
ADES equity earnings	14,450		9,138		25,500	22,313
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Distributions from equity method investees in excess of investment basis					25,500	22,313
Included in investing cash flows	14,450	$ 11,050	9,138	$ 13,175
Tinuum Services, LLC
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Gross profit (loss)	(21,701)		(17,249)		(42,707)	(30,128)
Operating, selling, general and administrative expenses	43,133		37,325		83,837	71,953
Income (loss) from operations	(64,834)		(54,574)		(126,544)	(102,081)
Other income	423		84		365	69
Loss attributable to noncontrolling interest	67,287		56,523		131,463	105,322
Net income available to members	2,876		2,033		5,284	3,310
ADES equity earnings	1,438		1,017		2,642	1,656
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Distributions from equity method investees, return on investment					2,700	2,875
Earnings from other
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
ADES equity earnings	$ 1		$ 0		$ 0	$ 0