CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net income	$ 152,189	$ 119,531
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	30,166	21,228
Operating lease right-of-use assets amortization expense	33,834	25,732
Bad debt expense	3,174	167
Deferred taxes	2,971	(1,193)
Stock-based compensation expense	31,320	37,553
Other	4,458	3,938
Changes in assets and liabilities:
Trade receivables and contract assets	(11,842)	(75,332)
Prepaid and other assets	1,216	1,690
Accounts payable	633	(2,069)
Accrued expenses and other liabilities	(5,835)	(42,075)
Operating lease liabilities	(30,857)	(25,705)
Income taxes payable	(2,016)	(19,638)
Net cash provided by operating activities	209,411	43,827
Cash flows from investing activities:
Purchases of property and equipment	(40,524)	(25,025)
Purchases of short-term investments	(60,000)	0
Acquisition of business, net of cash acquired (Note 2)	(12,573)	(16,240)
Purchases of non-marketable securities	(20,500)	(5,000)
Other investing activities, net	26	(1,180)
Net cash used in investing activities	(133,571)	(47,445)
Cash flows from financing activities:
Proceeds from stock option exercises	17,144	22,415
Payments of withholding taxes related to net share settlements of restricted stock units	(15,899)	(13,084)
Payment of contingent consideration for previously acquired business	(7,869)	(1,104)
Other financing activities, net	(24)	(19)
Net cash (used in)/provided by financing activities	(6,648)	8,208
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(11,999)	2,248
Net increase in cash, cash equivalents and restricted cash	57,193	6,838
Cash, cash equivalents and restricted cash, beginning of period	937,688	771,711
Cash, cash equivalents and restricted cash, end of period	$ 994,881	$ 778,549