Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
ASSETS
Cash and cash equivalents	$ 357,365	$ 350,945
Restricted Cash and Cash Equivalents, Current	402	0
Accounts receivable, net of allowances of $10,699 and $8,701, respectively	179,716	234,195
Prepaid expenses and other current assets	36,006	35,287
Total current assets	573,489	620,427
Long-term investments	70,215	57,722
Property and equipment, net	91,081	79,773
Trade names, net	126,229	123,947
Patent and patent licenses, net	8,843	10,871
Customer relationships, net	190,412	193,606
Goodwill	1,260,814	1,196,611
Other purchased intangibles, net	148,331	157,327
Other assets	11,245	12,809
Total assets	2,480,659	2,453,093
LIABILITIES AND STOCKHOLDERS’ EQUITY
Accounts payable and accrued expenses	143,246	169,837
Income taxes payable, current	3,807	0
Deferred revenue, current	(116,580)	(95,255)
Other current liabilities	289	10
Total current liabilities	263,922	265,102
Long-term debt	1,007,694	1,001,944
Deferred revenue, non-current	6,986	47
Accrued Income Taxes, Noncurrent	39,974	43,781
Liability for uncertain tax positions	54,496	52,216
Deferred income taxes, non-current	32,845	38,264
Other long-term liabilities	44,133	31,434
Total liabilities	1,450,050	1,432,788
Commitments and contingencies	0	0
Additional paid-in capital	338,409	325,854
Retained earnings	730,725	723,062
Accumulated other comprehensive loss	(39,005)	(29,090)
Stockholders' Equity Attributable to Parent	1,030,609	1,020,305
Total liabilities and stockholders’ equity	2,480,659	2,453,093
Common stock, $0.01 par value. Authorized 95,000,000; total issued and outstanding 47,994,805 and 47,854,510 shares, respectively	480	479
Series A Preferred Stock [Member]
LIABILITIES AND STOCKHOLDERS’ EQUITY
Preferred stock, $0.01 par value	0	0
Series B Preferred Stock [Member]
LIABILITIES AND STOCKHOLDERS’ EQUITY
Preferred stock, $0.01 par value	$ 0	$ 0