CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 421,818	$ 527,012
Accounts receivable, net of allowance for doubtful accounts of approximately $4,815 and $7,478 as of December 31, 2014 and 2015, respectively	40,276	38,694
Deferred and other income taxes, net	0	20,007
Income tax receivable	430	1,027
Prepaid expenses and other current assets	10,209	9,736
Total current assets	472,733	596,476
Long-term investments	15,507	17,151
Deferred income taxes, net	9,107	0
Property and equipment, net	88,311	73,753
Goodwill	1,252,945	1,138,805
Intangible assets, net	238,318	241,622
Deposits and other assets	2,650	2,676
Total assets	2,079,571	2,070,483
Current liabilities:
Current portion of long-term debt	16,746	16,665
Accounts payable	9,673	8,608
Accrued wages and commissions	31,045	23,155
Accrued expenses	31,469	27,001
Deferred gain on the sale of building	2,523	2,523
Deferred rent	1,687	0
Deferred revenue	42,138	38,003
Total current liabilities	135,281	115,955
Long-term debt, less current portion	338,366	355,136
Deferred gain on the sale of building	21,239	23,762
Deferred rent	29,628	27,032
Deferred income taxes, net	4,585	30,349
Income taxes payable	6,692	4,703
Total liabilities	$ 535,791	$ 556,937
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.01 par value; 2,000 shares authorized; none outstanding	$ 0	$ 0
Common stock, $0.01 par value; 60,000 shares authorized; 32,318 and 32,509 issued and outstanding as of December 31, 2014 and 2015, respectively	325	323
Additional paid-in capital	1,440,321	1,405,414
Accumulated other comprehensive loss	(7,594)	(6,384)
Retained earnings	110,728	114,193
Total stockholders’ equity	1,543,780	1,513,546
Total liabilities and stockholders’ equity	$ 2,079,571	$ 2,070,483