CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 12,613,000	$ (53,147,000)	$ (45,853,000)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	55,628,000	43,542,000	50,134,000
Gain on extinguishment of debt	0	(6,975,000)	0
Property and equipment impairment expense	0	6,305,000	36,609,000
Goodwill impairment expense	0	1,177,000	0
Deferred income tax expense (benefit)	3,430,000	(27,972,000)	(23,945,000)
Amortization of deferred revenue rebate	1,846,000	1,846,000	1,846,000
Amortization of deferred debt issuance costs	3,403,000	2,091,000	1,351,000
Stock-based compensation	9,489,000	1,649,000	1,239,000
Loss on disposal of assets	39,086,000	22,529,000	21,268,000
(Gain) loss on interest rate swap	(251,000)	(205,000)	260,000
Changes in operating assets and liabilities:
Accounts receivable	(84,477,000)	(24,888,000)	67,348,000
Other current assets	3,304,000	(563,000)	9,000
Inventories	(1,472,000)	3,859,000	(622,000)
Prepaid expenses	(468,000)	(62,000)	2,082,000
Accounts payable	64,228,000	37,049,000	(23,889,000)
Accrued liabilities	2,930,000	4,392,000	(6,295,000)
Accrued interest	(32,000)	32,000	(312,000)
Net cash provided by operating activities	109,257,000	10,659,000	81,230,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(285,891,000)	(42,832,000)	(62,855,000)
Proceeds from sale of assets	4,422,000	1,144,000	79,000
Net cash used in investing activities	(281,469,000)	(41,688,000)	(62,776,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from borrowings	60,045,000	0	60,718,000
Repayments of borrowings	(166,546,000)	(41,295,000)	(73,782,000)
Proceeds from insurance financing	4,125,000	4,126,000	4,105,000
Repayments of insurance financing	(3,807,000)	(4,527,000)	(6,257,000)
Extinguishment of debt	0	(30,000,000)	0
Payment of debt extinguishment costs	0	(525,000)	0
Payment of debt issuance costs	(1,653,000)	(140,000)	0
Proceeds from additional common equity capitalization	0	40,425,000	0
Proceeds from preferred equity capitalization	0	170,000,000	0
Payment of preferred equity capitalization costs	0	(7,489,000)	0
Proceeds from IPO	185,500,000	0	0
Payment of deferred IPO costs	(15,099,000)	(260,000)	0
Net cash provided by (used in) financing activities	62,565,000	130,315,000	(15,216,000)
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(109,647,000)	99,286,000	3,238,000
CASH AND CASH EQUIVALENTS — Beginning of year	133,596,000	34,310,000	31,072,000
CASH AND CASH EQUIVALENTS — End of year	$ 23,949,000	$ 133,596,000	$ 34,310,000