CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 282,810	$ 245,368	$ 181,848
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	24,129	18,989	16,005
Amortization	2,199	3,352	5,114
Stock-based compensation expense	20,516	21,412	14,469
Noncash lease expense	19,646	18,015	16,288
Deferred income tax benefit	(25,117)	(23,014)	(37,112)
Other	2,705	(2,127)	8
Changes in assets and liabilities:
Accounts receivable and unbilled, net	(48,282)	(66,920)	(24,982)
Prepaid expenses and other current assets	2,986	(10,175)	(9,134)
Accounts payable	1,051	6,431	1,866
Accrued expenses	82,080	52,476	26,156
Advanced billings	97,131	118,088	88,977
Lease liabilities	(18,873)	(15,899)	(15,632)
Other assets and liabilities, net	(9,607)	22,054	(544)
Net cash provided by operating activities	433,374	388,050	263,327
CASH FLOWS FROM INVESTING ACTIVITIES:
Property and equipment expenditures	(36,648)	(36,879)	(28,271)
Other	2,019	(1,863)	(3,093)
Net cash used in investing activities	(34,629)	(38,742)	(31,364)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from stock option exercises	11,378	22,074	17,643
Repurchases of common stock	(144,020)	(847,849)	(62,096)
Proceeds from revolving loan	105,000	324,200	0
Payments on revolving loan	(155,000)	(274,200)	0
Net cash used in financing activities	(182,642)	(775,775)	(44,453)
EFFECT OF EXCHANGE RATES ON CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	1,081	(6,572)	(3,972)
INCREASE (DECREASE) IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	217,184	(433,039)	183,538
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH — Beginning of period	28,265	461,304	277,766
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH — End of period	245,449	28,265	461,304
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION—
Cash paid during the period for income taxes	76,353	50,164	56,243
Cash paid during the period for interest	3,056	2,935	123
Acquisition of property and equipment—non-cash	$ 5,254	$ 7,838	$ 6,352