Unaudited Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash Flows From Operating Activities:
Net income (loss)	$ 15,631	$ (40,147)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	79,503	78,448
Amortization of debt issuance costs and discounts	1,773	2,311
Loss on sale or disposal of assets, net	550	7,651
Deferred income tax provision (benefit)	5,463	(11,823)
Equity-based compensation	7,282	13,437
Changes in assets and liabilities:
Accounts receivable	(7,033)	(43,858)
Inventories	(7,399)	(8,882)
Prepaid expenses and other current assets	976	(558)
Accounts payable and accrued expenses	15,167	22,487
Accrued salaries, wages and benefits	(6,216)	7,783
Deferred revenue	64,052	87,724
Other accrued liabilities	(2,989)	13,050
Right-of-use assets and operating lease obligations	263
Other assets and liabilities	363	(809)
Net cash provided by operating activities	167,386	126,814
Cash Flows From Investing Activities:
Capital expenditures	(112,738)	(97,372)
Other investing activities	(52)	(477)
Net cash used in investing activities	(112,790)	(97,849)
Cash Flows From Financing Activities:
Repayments of long-term debt	(7,753)	(11,854)
Proceeds from draws on revolving credit facility	219,000	55,000
Repayments of revolving credit facility	(104,000)	(70,000)
Purchase of treasury stock	(150,000)
Payment of tax withholdings on equity-based compensation through shares withheld	(3,968)	(2,269)
Exercise of stock options	2,335	1,185
Other financing activities	(398)	(304)
Net cash used in financing activities	(44,784)	(28,242)
Change in Cash and Cash Equivalents, including Restricted Cash	9,812	723
Cash and Cash Equivalents, including Restricted Cash—Beginning of period	35,007	33,997
Cash and Cash Equivalents, including Restricted Cash—End of period	44,819	34,720
Supplemental Disclosure of Noncash Investing Activities:
Capital expenditures in accounts payable	$ 28,553	$ 32,715