CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues
Revenues	$ 879,112	$ 909,781	$ 856,396	$ 765,439	$ 663,062	$ 610,506	$ 564,245	$ 605,253	$ 3,410,728	$ 2,443,066	$ 1,865,045
Operating expenses
Cost of revenues (excluding depreciation)									3,003,116	2,054,627	1,636,339
Operating expense (excluding depreciation)									215,284	202,016	169,371
Depreciation, depletion, and amortization									52,642	45,989	31,617
General and administrative expense (excluding depreciation)									47,426	46,078	42,073
Acquisition and integration costs									10,319	395	5,294
Total operating expenses									3,328,787	2,349,105	1,884,694
Operating income (loss)	20,408	4,894	28,983	27,656	21,605	26,716	16,451	29,189	81,941	93,961	(19,649)
Other income (expense)
Interest expense and financing costs, net									(39,768)	(31,632)	(28,506)
Debt extinguishment and commitment costs									(4,224)	(8,633)	0
Gain on curtailment of pension obligation									0	0	3,067
Other income (expense), net									1,046	911	(10)
Change in value of common stock warrants									1,801	(1,674)	2,962
Change in value of contingent consideration									(10,500)	0	10,770
Equity earnings (losses) from Laramie Energy, LLC									9,464	18,369	(22,381)
Total other expense, net									(42,181)	(22,659)	(34,098)
Income (loss) before income taxes									39,760	71,302	(53,747)
Income tax benefit (expense)									(333)	1,319	7,912
Net income (loss)	$ 13,886	$ (5,822)	$ 16,178	$ 15,185	$ 19,005	$ 18,824	$ 7,006	$ 27,786	$ 39,427	$ 72,621	$ (45,835)
Income (loss) per share
Basic (USD per share)	$ 0.30	$ (0.13)	$ 0.35	$ 0.33	$ 0.41	$ 0.41	$ 0.15	$ 0.60	$ 0.85	$ 1.58	$ (1.08)
Diluted (USD per share)	$ 0.30	$ (0.13)	$ 0.35	$ 0.33	$ 0.41	$ 0.41	$ 0.15	$ 0.58	$ 0.85	$ 1.57	$ (1.08)
Weighted-average number of shares outstanding
Basic (in shares)									45,726	45,543	42,349
Diluted (in shares)									45,755	45,583	42,349