Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 128,435	$ 93,519
Marketable securities	269,351	281,285
Accounts receivable, net of allowance for doubtful accounts	105,961	115,216
Prepaid commission expense	4,115	1,842
Prepaid expenses and other current assets	34,997	20,382
Deferred income taxes	0	6,536
Total current assets	542,859	518,780
Restricted cash	5,515	5,760
Furniture, fixtures and equipment, net	81,619	58,461
Marketable securities- long-term	155,826	140,418
Goodwill	47,913	30,780
Intangible assets, net	18,801	5,090
Deferred income taxes- long-term	37,697	40,415
Other assets	23,484	18,181
Total assets	913,714	817,885
Current liabilities:
Accounts payable	2,408	6,202
Accrued payroll and other compensation	29,455	29,260
Accrued expenses and other	35,438	20,958
1.00% convertible senior notes, net	80,319	75,911
Convertible Debt, Current	274,345	0
Total current liabilities	421,965	132,331
Noncurrent liabilities:
1.00% convertible senior notes, net	0	263,401
Deferred revenue, less current portion	2,926	1,703
Deferred tax liabilities	124	322
Other long-term liabilities	21,011	18,138
Total noncurrent liabilities	24,061	283,564
Total liabilities	446,026	415,895
Commitments and contingencies
Stockholders' equity:
Preferred stock	0	0
Common stock	626	614
Additional paid-in capital	467,645	418,497
Treasury stock	(130,499)	(114,204)
Accumulated other comprehensive loss	(3,055)	(5,276)
Retained earnings	132,971	102,359
Total stockholders' equity	467,688	401,990
Total liabilities and stockholders' equity	$ 913,714	$ 817,885