Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net income	$ 40,653	$ 32,113
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	48,778	39,536
Amortization of debt issuance cost	970	400
Equity-based compensation	2,338	2,427
Change in deferred income taxes	5,710	(203)
(Gain) loss on disposal of assets, net	6,634	(6,146)
Changes in operating assets and liabilities:
Accounts receivable, net	4,453	2,009
Income taxes receivable	4,549	4,547
Prepaid and other current assets	(8,576)	(3,336)
Accounts payable and accrued liabilities	(11,663)	(7,977)
Deferred revenue	2,772	527
Income taxes payable		14,758
Other assets and liabilities, net	(1,926)	(395)
Net cash provided by operating activities	94,692	78,260
Cash flows from investing activities:
Capital expenditures	(41,019)	(35,917)
Change in accrued expenses related to capital expenditures	(4,826)	(1,143)
Proceeds from sales of property, plant and equipment	226	10,075
Net cash used in investing activities	(45,619)	(26,985)
Cash flows from financing activities:
Payments on long-term debt	(2,816)	(1,254)
Repurchases of common stock	(2,295)	(399)
Payment of withholding tax for equity awards	(7,199)	(331)
Dividends paid to stockholders	(10,035)	(8,579)
Change in cash overdraft	(2,987)	(5,285)
Net cash used in financing activities	(25,332)	(15,848)
Change in cash and cash equivalents	23,741	35,427
Cash and cash equivalents, beginning of period	161,752	138,040
Cash and cash equivalents, end of period	185,493	173,467
Supplemental cash flow disclosures:
Cash paid for interest, net of capitalized interest	7,072	743
Cash paid for income taxes, net of refunds	$ 35	$ 42