CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 1,266,614	$ 1,322,143
Short-term investments	0	60,007
Trade receivables and contract assets, net of allowance of $6,207 and $4,886, respectively	755,588	501,062
Prepaid and other current assets	69,992	29,570
Total current assets	2,092,194	1,912,782
Restricted cash, noncurrent	158,454	1,284
Property and equipment, net	176,881	169,533
Operating lease right-of-use assets, net	192,628	228,672
Intangible assets, net	74,576	51,975
Goodwill	386,508	211,956
Deferred tax assets	104,057	92,454
Other noncurrent assets	56,935	52,676
Total assets	3,242,233	2,721,332
Current liabilities
Accounts payable	8,086	10,189
Accrued compensation and benefits expenses	412,061	294,709
Accrued expenses and other current liabilities	140,298	79,690
Income taxes payable, current	20,928	20,603
Operating lease liabilities, current	51,174	60,759
Total current liabilities	632,547	465,950
Long-term debt	25,024	25,038
Income taxes payable, noncurrent	42,193	43,448
Operating lease liabilities, noncurrent	149,556	180,604
Other noncurrent liabilities	53,794	23,274
Total liabilities	903,114	738,314
Commitments and contingencies (Note 12)
Stockholders’ equity
Common stock, $0.001 par value; 160,000 shares authorized; 56,728 and 56,128 shares issued, 56,708 and 56,108 shares outstanding at September 30, 2021 and December 31, 2020, respectively	57	56
Additional paid-in capital	693,887	660,771
Retained earnings	1,687,253	1,347,880
Treasury stock	(177)	(177)
Accumulated other comprehensive loss	(41,901)	(25,512)
Total stockholders’ equity	2,339,119	1,983,018
Total liabilities and stockholders’ equity	$ 3,242,233	$ 2,721,332