CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net income	$ 109,046	$ 85,565
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	17,807	14,940
Operating lease right-of-use assets amortization expense	15,676	16,816
Bad debt expense	2,925	2,719
Deferred taxes	6,692	8,288
Stock-based compensation expense	24,553	11,881
Other	(4,926)	5,893
Changes in assets and liabilities:
Trade receivables and contract assets	(89,395)	(51,423)
Prepaid and other assets	(8,581)	(9,746)
Accounts payable	(3,166)	(2,407)
Accrued expenses and other liabilities	(15,830)	5,437
Operating lease liabilities	(16,065)	(15,646)
Income taxes payable	(25,909)	(9,062)
Net cash provided by operating activities	12,827	63,255
Cash flows from investing activities:
Purchases of property and equipment	(11,186)	(29,075)
Proceeds from short-term investments	60,000	0
Acquisition of business, net of cash acquired (Note 2)	0	(10,339)
Purchases of non-marketable securities	(1,044)	(20,000)
Other investing activities, net	691	(71)
Net cash provided by/(used in) investing activities	48,461	(59,485)
Cash flows from financing activities:
Proceeds from stock option exercises	4,373	6,850
Payments of withholding taxes related to net share settlements of restricted stock units	(3,304)	(1,018)
Payment of contingent consideration for previously acquired business	0	(7,869)
Other financing activities, net	260	(9)
Net cash provided by/(used in) financing activities	1,329	(2,046)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(11,856)	(22,009)
Net increase/(decrease) in cash, cash equivalents and restricted cash	50,761	(20,285)
Cash, cash equivalents and restricted cash, beginning of period	1,323,533	937,688
Cash, cash equivalents and restricted cash, end of period	$ 1,374,294	$ 917,403