Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income (loss)	$ 22,579	$ 7,775	$ (39,164)
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense	30,532	20,230	16,162
Depreciation	61,871	55,948	52,742
Amortization of intangibles	53,054	52,302	43,983
Amortization of debt issuance costs and debt discount	4,743	4,598	3,138
Deferred income taxes	12,167	(3,276)	(12,495)
Restructuring expense, non-cash	0	0	7,075
Change in fair value of acquisition-related contingent consideration	3,076	115	7,212
Other	477	(877)	621
Changes in assets and liabilities:
Accounts receivable	(16,002)	(35,109)	3,280
Prepaid expenses and other current assets	824	(489)	(20,002)
Income taxes receivable, net	(20,175)	5,979	2,208
Other assets	(3,845)	(5,096)	(4,209)
Accounts payable and accrued expenses	14,733	10,608	(6,007)
Accrued compensation	4,267	9,329	9,292
Other current and non-current liabilities	(6,728)	(6,044)	19,891
Deferred revenue	(15,054)	(6,964)	6,674
Payment for acquisition-related contingent consideration	(160)	(2,549)	0
Net cash provided by operating activities	146,359	106,480	90,401
Cash flows from investing activities:
Maturities of short-term investments	0	6,964	96,588
Sales of short-term investments	0	0	161,772
Purchases of property and equipment	(22,709)	(22,809)	(25,505)
Investment in capitalized software	(44,008)	(36,130)	(39,469)
Purchase of intangible assets	(19,893)	0	0
Acquisition, net of cash acquired of $—, $— and $23,850, respectively	0	0	(1,082,740)
Net cash used in investing activities	(86,610)	(51,975)	(889,354)
Cash flows from financing activities:
Proceeds from credit facility borrowings, net of discount	99,000	0	965,300
Repayment of credit facility borrowings	(108,800)	(59,800)	(238,700)
Payments for debt issuance costs	(1,000)	0	(18,269)
Proceeds from exercise of stock options	198	3,669	1,833
Finance lease liabilities paid	(3,481)	(2,393)
Finance lease liabilities paid			(1,201)
Tax payments for equity award issuances	(11,357)	(5,878)	(3,363)
Payment for acquisition-related contingent consideration	(3,523)	(12,600)	0
Net cash (used in) provided by financing activities	(28,963)	(77,002)	705,600
Increase (Decrease) in cash and cash equivalents	30,786	(22,497)	(93,353)
Cash and cash equivalents, beginning of period	93,094	115,591	208,944
Cash and cash equivalents, end of period	123,880	93,094	115,591
Supplemental cash flow disclosure:
Income taxes paid (received), net	1,396	(4,588)	(4,136)
Interest paid	52,516	62,768	43,573
Non-cash transactions:
Accruals of purchases of property, equipment	7,604	3,156	12,097
Accruals for investment in capitalized software	6,771	1,948	1,495
Accruals for purchase of intangible assets	2,553	0	0
Leasehold improvement paid by lessor	482	2,906	0
Acquisition consideration	$ 0	$ 0	$ 84,156