CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 171,899	$ 68,363
Marketable securities	293,269	0
Total cash, cash equivalents, and marketable securities	465,168	68,363
Accounts receivable	215,827	199,720
Unbilled receivables	207,155	180,219
Other current assets	88,760	57,308
Total current assets	976,910	505,610
Unbilled receivables	113,278	121,736
Goodwill	79,231	79,039
Other long-term assets	434,843	278,427
Total assets	1,604,262	984,812
Current liabilities:
Accounts payable	24,028	17,475
Accrued expenses	59,261	48,001
Accrued compensation and related expenses	123,012	104,126
Deferred revenue	232,865	190,080
Other current liabilities	20,969	18,273
Total current liabilities	460,135	377,955
Convertible senior notes, net	518,203	0
Operating lease liabilities	59,053	52,610
Other long-term liabilities	24,699	15,237
Total liabilities	1,062,090	445,802
Commitments and Contingencies
Stockholders’ equity:
Preferred stock, $0.01 par value, 1,000 shares authorized; none issued	0	0
Common stock, $0.01 par value, 200,000 shares authorized; 80,890 and 79,599 shares issued and outstanding at December 31, 2020 and 2019, respectively	809	796
Additional paid-in capital	204,432	140,523
Retained earnings	339,879	410,919
Accumulated other comprehensive (loss)
Net unrealized gain on available-for-sale marketable securities, net of tax	46	0
Foreign currency translation adjustments	(2,994)	(13,228)
Total stockholders’ equity	542,172	539,010
Total liabilities and stockholders’ equity	$ 1,604,262	$ 984,812