CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net loss	$ 39,427,000	$ 72,621,000	$ (45,835,000)
Adjustments to reconcile net income (loss) to cash provided by (used in) operating activities:
Depreciation, depletion, and amortization	52,642,000	45,989,000	31,617,000
Debt extinguishment and commitment costs	4,224,000	8,633,000	0
Non-cash interest expense	7,127,000	7,276,000	18,121,000
Change in value of common stock warrants	(1,801,000)	1,674,000	(2,962,000)
Change in value of contingent consideration	0	0	(10,770,000)
Deferred taxes	661,000	(1,321,000)	(7,935,000)
Stock-based compensation	6,196,000	7,204,000	6,625,000
Unrealized (gain) loss on derivative contracts	2,122,000	(989,000)	(15,479,000)
Equity (earnings) losses from Laramie Energy, LLC	(9,464,000)	(18,369,000)	22,381,000
Net changes in operating assets and liabilities:
Trade accounts receivable	(35,790,000)	(19,100,000)	(17,162,000)
Collateral posted with broker for derivative transactions	(3,790,000)	2,499,000	18,212,000
Prepaid and other assets	(5,521,000)	37,645,000	945,000
Inventories	31,840,000	(146,533,000)	49,015,000
Deferred turnaround expenditures	0	0	(32,661,000)
Obligations under inventory financing agreements	(17,138,000)	143,034,000	(5,977,000)
Accounts payable and other accrued liabilities	19,885,000	(33,780,000)	(26,698,000)
Contingent consideration	0	0	(4,830,000)
Net cash provided by (used in) operating activities	90,620,000	106,483,000	(23,393,000)
Cash flows from investing activities:
Acquisitions, net of cash acquired	(128,198,000)	0	(209,183,000)
Capital expenditures	(48,439,000)	(31,708,000)	(24,833,000)
Proceeds from sale of assets	816,000	35,000	2,773,000
Investment in Laramie Energy, LLC	0	0	(55,000,000)
Net cash used in investing activities	(175,821,000)	(31,673,000)	(286,243,000)
Cash flows from financing activities:
Proceeds from sale of common stock, net of offering costs	19,318,000	0	49,044,000
Proceeds from borrowings	118,741,000	616,706,000	354,682,000
Repayments of borrowings	(118,751,000)	(603,770,000)	(202,165,000)
Net borrowings (repayments) on deferred payment arrangement	27,264,000	(2,198,000)	8,027,000
Payment of deferred loan costs	(379,000)	(10,064,000)	(6,892,000)
Contingent consideration settlements	0	0	(11,980,000)
Payments for early termination of financing agreements	0	(4,432,000)	0
Payments for commitment costs	(3,390,000)	0	0
Other financing activities, net	(860,000)	(993,000)	(598,000)
Net cash provided by (used in) financing activities	41,943,000	(4,751,000)	190,118,000
Net increase (decrease) in cash, cash equivalents, and restricted cash	(43,258,000)	70,059,000	(119,518,000)
Cash, cash equivalents, and restricted cash at beginning of period	119,077,000	49,018,000	168,536,000
Cash, cash equivalents, and restricted cash at end of period	75,819,000	119,077,000	49,018,000
Net cash paid for:
Interest	(28,186,000)	(23,873,000)	(13,217,000)
Taxes	49,000	(1,478,000)	589,000
Non-cash investing and financing activities:
Accrued capital expenditures	6,199,000	2,926,000	4,907,000
Value of warrants and debt reclassified to equity	0	0	3,084,000
Capital lease additions	$ 1,678,000	$ 165,000	$ 1,575,000