CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net income	$ 481,652	$ 327,160	$ 261,057
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	83,401	62,874	45,317
Operating lease right-of-use assets amortization expense	61,750	66,369	55,859
Bad debt expense	2,488	2,253	1,619
Deferred taxes	(46,900)	(19,994)	(7,764)
Stock-based compensation expense	111,655	75,238	72,036
Other	13,137	6,796	4,764
Changes in assets and liabilities:
Trade receivables and contract assets	(211,684)	4,235	(87,174)
Prepaid and other assets	(16,182)	6,983	(7,155)
Accounts payable	(2,403)	2,428	(1,685)
Accrued expenses and other liabilities	155,657	60,133	27,125
Operating lease liabilities	(63,812)	(64,453)	(53,419)
Income taxes payable	3,568	14,385	(23,127)
Net cash provided by operating activities	572,327	544,407	287,453
Cash flows from investing activities:
Purchases of property and equipment	(111,501)	(68,793)	(99,308)
Purchases of short-term investments	0	(120,000)	0
Proceeds from short-term investments	60,000	60,009	0
Acquisition of businesses, net of cash acquired	(314,958)	(18,888)	(39,322)
Purchases of non-marketable securities	(2,544)	(20,500)	(5,000)
Other investing activities, net	79	1,018	(1,739)
Net cash used in investing activities	(368,924)	(167,154)	(145,369)
Cash flows from financing activities:
Proceeds from stock option exercises	26,286	26,410	37,003
Payments of withholding taxes related to net share settlements of restricted stock units	(41,598)	(20,132)	(15,503)
Proceeds from debt	31,109	0	0
Repayment of debt	(31,054)	(18)	(9)
Payment of contingent consideration for previously acquired businesses	(40,227)	(7,004)	(1,104)
Purchase of noncontrolling interest	(1,749)	0	0
Other financing activities, net	(2,324)	(21)	(24)
Net cash (used in)/provided by financing activities	(59,557)	(765)	20,363
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(18,032)	9,357	3,530
Net increase in cash, cash equivalents and restricted cash	125,814	385,845	165,977
Cash, cash equivalents and restricted cash, beginning of period	1,323,533	937,688	771,711
Cash, cash equivalents and restricted cash, end of period	1,449,347	1,323,533	937,688
Cash paid during the year for:
Income taxes, net of refunds	87,317	54,520	65,306
Interest	413	425	832
Supplemental disclosure of non-cash investing and financing activities
Acquisition-date fair value of contingent consideration issued for acquisition of businesses	57,249	7,119	3,876
Capital expenditures incurred but not yet paid	$ 7,738	$ 1,582	$ 16,921