CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net income	$ 241,621	$ 186,533
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	46,095	32,355
Operating lease right-of-use assets amortization expense	50,467	40,203
Bad debt expense	2,794	133
Deferred taxes	(4,546)	(3,105)
Stock-based compensation expense	54,794	53,024
Other	3,225	7,522
Changes in assets and liabilities:
Trade receivables and contract assets	3,477	(77,833)
Prepaid and other assets	4,261	237
Accounts payable	1,836	(1,844)
Accrued expenses and other liabilities	30,787	(11,230)
Operating lease liabilities	(47,023)	(39,230)
Income taxes payable	(2,813)	(23,899)
Net cash provided by operating activities	384,975	162,866
Cash flows from investing activities:
Purchases of property and equipment	(50,311)	(52,295)
Purchases of short-term investments	(60,000)	0
Acquisition of business, net of cash acquired (Note 2)	(18,888)	(28,655)
Purchases of non-marketable securities	(20,500)	(5,000)
Other investing activities, net	452	(1,632)
Net cash used in investing activities	(149,247)	(87,582)
Cash flows from financing activities:
Proceeds from stock option exercises	23,027	28,798
Payments of withholding taxes related to net share settlements of restricted stock units	(16,213)	(14,521)
Payment of contingent consideration for previously acquired business	(7,869)	(1,104)
Other financing activities, net	(28)	(26)
Net cash (used in)/provided by financing activities	(1,083)	13,147
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(10,110)	(5,753)
Net increase in cash, cash equivalents and restricted cash	224,535	82,678
Cash, cash equivalents and restricted cash, beginning of period	937,688	771,711
Cash, cash equivalents and restricted cash, end of period	$ 1,162,223	$ 854,389