Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities:
Net loss	$ (31,081)	$ (429,667)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization expense	42,429	51,055
Impairments of goodwill	0	406,056
Impairments of inventories	0	25,230
Impairments of fixed and lease assets	3,444	8,190
Stock-based compensation expense	4,703	3,257
Amortization of debt discount and deferred financing costs	1,366	4,067
Deferred income tax benefit	(6,834)	(48,738)
Gains on extinguishment of 1.50% convertible senior notes	(4,022)	(4,779)
Gains on disposals of assets	(1,632)	(1,489)
Other, net	375	3,177
Changes in operating assets and liabilities:
Accounts receivable	(6,962)	56,062
Inventories	(4,458)	(4,320)
Accounts payable and accrued liabilities	11,896	(34,227)
Deferred revenue	1,780	5,991
Other operating assets and liabilities, net	2,929	4,266
Net cash flows provided by operating activities	13,933	44,131
Cash flows from investing activities:
Capital expenditures	(7,311)	(8,915)
Proceeds from disposition of property and equipment	3,422	5,418
Other, net	(326)	(301)
Net cash flows used in investing activities	(4,215)	(3,798)
Cash flows from financing activities:
Revolving credit facility borrowings	12,571	72,173
Revolving credit facility repayments	(31,571)	(53,104)
Issuance of 4.75% convertible senior notes	135,000	0
Purchases of 1.50% convertible senior notes	(125,952)	(10,595)
Other debt and finance lease activity, net	119	(165)
Payment of financing costs	(7,779)	(651)
Shares added to treasury stock as a result of net share settlements due to vesting of stock awards	(1,500)	(2,667)
Net cash flows provided by (used in) financing activities	(19,112)	4,991
Effect of exchange rate changes on cash and cash equivalents	33	2
Net change in cash and cash equivalents	(9,361)	45,326
Cash and cash equivalents, beginning of period	72,011	8,493
Cash and cash equivalents, end of period	62,650	53,819
Cash paid for:
Interest	2,256	3,486
Income taxes, net	$ 920	$ 2,888