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 (loss) income	$ (293,623)	$ 66,048	$ 43,793
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	18,430	13,573	9,806
Loss on extinguishment of debt		4,877	2,857
Amortization of debt issuance costs	3,390	3,381	1,239
Non-cash operating lease expense	4,478	2,150
Stock-based compensation	397,285	3,747	1,762
Change in fair value of contingent consideration	2,068
Deferred income taxes	(10,910)	(5,674)	(2,433)
Loss on abandonment and impairment of operating lease assets	961
Charitable stock donation	41,721
Changes in operating assets and liabilities, net of effect of business acquisitions
Accounts receivable	(16,139)	(14,517)	(12,843)
Prepaid expenses and other assets	(40,935)	102	(2,627)
Accounts payable	2,154	515	665
Accrued expenses and other current liabilities	15,010	11,225	77
Operating lease liabilities	4,576	(2,309)
Other liabilities	2,875	168	2,957
Net cash provided by operating activities	131,341	83,286	45,253
Cash flows from investing activities
Purchase of property and equipment	(20,553)	(1,425)	(804)
Acquisitions, net of cash acquired	(55,793)	(31,306)
Capitalized software	(15,271)	(4,324)	(2,654)
Net cash used in investing activities	(91,617)	(37,055)	(3,458)
Cash flows from financing activities
Proceeds from issuance of common stock in initial public offering, net of underwriting discounts and commissions	891,793
Proceeds from private placement with a related party	100,000
Proceeds from long-term debt	28,000	154,613	901,813
Payments on long-term debt	(35,029)	(211,845)	(294,937)
Payment of debt issuance costs and prepayment penalty	(1,306)	(2,214)	(25,613)
Issuance of preferred stock, net			737,009
Issuance of common stock		1,623
Dividends paid			(1,346,355)
Payments of initial public offering issuance costs	(4,937)
Proceeds from exercise of stock options	5,343	3,042	3,349
Proceeds from early exercise of stock options	667
Employee taxes paid related to net share settlement of equity awards	(78,714)
Net cash provided by (used in) financing activities	905,817	(54,781)	(24,734)
Net change in cash, cash equivalents and restricted cash	945,541	(8,550)	17,061
Cash, cash equivalents and restricted cash
Beginning of year	26,050	34,600	17,539
End of year	971,591	26,050	34,600
Supplemental disclosure of cash flow information
Income taxes	29,228	19,400	11,700
Interest	24,517	48,443	18,658
Non cash investing and financing activities
Purchase of property and equipment included in accounts payable and accrued expenses and other current liabilities	2,100
Right-of-use assets obtained in exchange for new operating lease liabilities	234	29,493
Stock-based compensation included in capitalized software development costs	2,437	385
Capitalized software development costs in accrued expenses and other current liabilities	1,273
Conversion of preferred stock to common stock	737,009		166,777
Reconciliation of cash, cash equivalents and restricted cash to the consolidated balance sheets
Cash and cash equivalents	968,691	26,050	34,600
Restricted cash	2,900
End of year	$ 971,591	$ 26,050	$ 34,600