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	$ 454,627	$ 433,887	$ 451,295
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	106,867	85,275	60,516
Operating lease right-of-use assets expense	22,193	20,971	18,459
Deferred income tax benefit	(34,490)	(30,932)	(14,511)
Provision for bad debts	1,006	6,438	2,928
Stock-based compensation expense	166,338	145,615	116,190
Gain on equity investment	(15,139)	0	0
Other	2,708	2,180	2,778
Changes in operating assets and liabilities:
Accounts receivable	(149,017)	(160,319)	(154,403)
Other receivables and current assets	(64,316)	(2,312)	(26,182)
Other long-term assets	(3,217)	(14,818)	(5,622)
Accounts payable, accrued expenses and current liabilities	53,846	21,362	38,543
Accrued income taxes	(18,429)	19,713	575
Deferred revenue	26,547	5,448	17,245
Other long-term liabilities	(42)	14,802	(7,875)
Net cash provided by operating activities	549,482	547,310	499,936
Cash flows from investing activities:
Acquisitions, net of cash acquired	(510,805)	(572,328)	(787,196)
Capital expenditures	(23,018)	(35,370)	(44,940)
Other investing activities	(2,990)	(6,555)	(1,412)
Net cash used in investing activities	(536,813)	(614,253)	(833,548)
Cash flows from financing activities:
Proceeds from long-term debt	0	375,000	500,000
Principal payments on long-term debt	(45,000)	(75,000)	0
Purchase of treasury stock	(134,679)	(161,029)	(59,116)
Restricted stock withholding taxes paid in lieu of issued shares	(97,037)	(71,019)	(42,431)
Proceeds from shares issued for stock-based compensation	31,377	29,560	34,093
Other financing activities	(513)	(915)	(3,137)
Net cash (used in) provided by financing activities	(245,852)	96,597	429,409
Effect of exchange rate fluctuations on cash and cash equivalents	(11,822)	10,924	(842)
Net (decrease) increase in cash and cash equivalents	(245,005)	40,578	94,955
Cash and cash equivalents, beginning of period	912,672	872,094	777,139
Cash and cash equivalents, end of period	667,667	912,672	872,094
Supplemental disclosures of cash flow information:
Income taxes paid	130,426	54,174	86,770
Interest paid	11,146	11,941	787
Fair value of common stock issued and unpaid consideration in connection with acquisitions	$ 0	$ 232,690	$ 307,173