Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 92,487	$ 90,545
Short-term investments	74,893	73,075
Accounts receivable, net of allowance for doubtful accounts of $141 and $139 at March 31, 2013 and December 31, 2012, respectively	42,124	48,980
Deferred tax assets	3,529	3,732
Other current assets	10,883	10,796
Total current assets	223,916	227,128
Long-term assets:
Property and equipment, net	7,647	7,361
Long-term investments	37,435	30,102
Restricted cash	584	584
Intangible assets, net	10,410	11,247
Goodwill	37,250	37,529
Other long-term assets	19,486	12,955
Total long-term assets	112,812	99,778
Total assets	336,728	326,906
Current liabilities:
Accounts payable and accrued expenses	12,704	15,686
Notes payable and bank loans, current portion	539	555
Deferred revenue, current portion	56,100	49,368
Total current liabilities	69,343	65,609
Convertible senior notes	87,689	86,451
Notes payable and bank loans	402	414
Deferred revenue	3,480	11,781
Other long-term liabilities	1,477	1,416
Total liabilities	162,391	165,671
Commitments and contingencies (Note 8)
Stockholders' equity:
Preferred stock, $0.01 par value per share; 5,000,000 shares authorized at March 31, 2013 and December 31, 2012; no shares issued and outstanding at March 31, 2013 and December 31, 2012
Common stock, par value $0.01 per share; 100,000,000 shares authorized at March 31, 2013 and December 31, 2012; 28,023,873 and 27,913,471 shares issued and outstanding at March 31, 2013 and December 31, 2012, respectively	280	279
Additional paid-in capital	224,124	208,073
Accumulated other comprehensive loss	(3,641)	(3,008)
Accumulated deficit	(46,426)	(44,109)
Total stockholders' equity	174,337	161,235
Total liabilities and stockholders' equity	$ 336,728	$ 326,906