CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 159,965	$ 171,899
Marketable securities	202,814	293,269
Total cash, cash equivalents, and marketable securities	362,779	465,168
Accounts receivable	182,717	215,827
Unbilled receivables	226,714	207,155
Other current assets	68,008	88,760
Total current assets	840,218	976,910
Long-term unbilled receivables	129,789	113,278
Goodwill	81,923	79,231
Other long-term assets	541,601	434,843
Total assets	1,593,531	1,604,262
Current liabilities:
Accounts payable	15,281	24,028
Accrued expenses	63,890	59,261
Accrued compensation and related expenses	120,946	123,012
Deferred revenue	275,844	232,865
Other current liabilities	9,443	20,969
Total current liabilities	485,404	460,135
Convertible senior notes, net	590,722	518,203
Operating lease liabilities	87,818	59,053
Other long-term liabilities	13,499	24,699
Total liabilities	1,177,443	1,062,090
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; 81,712 and 80,890 shares issued and outstanding as of December 31, 2021 and 2020, respectively	817	809
Additional paid-in capital	145,810	204,432
Retained earnings	276,449	339,879
Accumulated other comprehensive (loss)
Net unrealized gain on available-for-sale securities, net of tax	686	46
Foreign currency translation adjustments	(7,674)	(2,994)
Total stockholders’ equity	416,088	542,172
Total liabilities and stockholders’ equity	$ 1,593,531	$ 1,604,262