Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities
Net income (loss)	$ (18,784)	$ 13,260
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	135,297	136,015
Provision for losses on accounts receivable	895	2,960
Stock-based compensation expense	33,522	24,245
Amortization of debt issuance costs	4,498	4,570
Deferred taxes	(17,527)	(16,032)
(Gain) loss on foreign currency exchange rates	(674)	1,639
Other non-cash expenses (benefits)	1,033	(900)
Changes in operating assets and liabilities, net of assets acquired and liabilities assumed in business combinations:
Accounts receivable	15,455	13,854
Income taxes receivable	(2,446)	(104)
Prepaid and other assets	(8,492)	(1,224)
Accounts payable	(7,441)	(2,794)
Accrued liabilities and other	(2,791)	1,239
Accrued interest payable	(4)	(89)
Income taxes payable	(30,491)	4,022
Deferred revenue	(18,736)	3,363
Other long-term liabilities	(276)	66
Net cash provided by operating activities	83,038	184,090
Cash flows from investing activities
Purchases of property and equipment	(18,124)	(12,123)
Purchases of intangible assets	(3,823)	(4,182)
Acquisitions, net of cash acquired	447	0
Net cash used in investing activities	(21,500)	(16,305)
Cash flows from financing activities
Proceeds from issuance of common stock under employee stock purchase plan	3,129	2,357
Repurchase of common stock and incentive restricted stock	(10,059)	(2,376)
Exercise of stock options	401	309
Repayments of borrowings from credit agreement	(9,950)	(9,950)
Payment of debt issuance costs	(903)	0
Net cash used in financing activities	(17,382)	(9,660)
Effect of exchange rate changes on cash and cash equivalents	(4,019)	(83)
Net increase in cash and cash equivalents	40,137	158,042
Cash and cash equivalents
Beginning of period	370,498	173,372
End of period	410,635	331,414
Supplemental disclosure of cash flow information
Cash paid for interest	27,995	38,149
Cash paid for income taxes	$ 35,715	$ 16,755