Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
ASSETS
Cash and cash equivalents	$ 209,474	$ 350,945
Accounts receivable, net of allowances of $10,422 and $8,701, respectively	221,615	234,195
Prepaid expenses and other current assets	29,242	35,287
Total current assets	460,331	620,427
Long-term investments	83,828	57,722
Property and equipment, net	98,813	79,773
Trade names, net	142,888	123,947
Patent and patent licenses, net	7,346	10,871
Customer relationships, net	191,208	193,606
Goodwill	1,380,376	1,196,611
Other purchased intangibles, net	185,026	157,327
Other assets	11,014	12,809
TOTAL ASSETS	2,560,830	2,453,093
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable and accrued expenses	166,521	169,837
Income taxes payable, current	12,915	0
Deferred revenue, current	127,568	95,255
Other current liabilities	318	10
Total current liabilities	307,322	265,102
Long-term debt	1,013,129	1,001,944
Deferred revenue, noncurrent	13,200	47
Income taxes payable, noncurrent	11,675	43,781
Liability for uncertain tax positions	59,644	52,216
Deferred income taxes, noncurrent	69,048	38,264
Other long-term liabilities	51,068	31,434
TOTAL LIABILITIES	1,525,086	1,432,788
Commitments and contingencies	0	0
Common stock, $0.01 par value. Authorized 95,000,000 at December 31, 2018 and 2017; total issued 48,082,800 and 47,854,510 shares at December 31, 2018 and 2017, respectively; total outstanding 47,482,800 and 47,854,510 shares at December 31, 2018 and 2017, respectively.	481	479
Additional paid-in capital	354,210	325,854
Treasury stock, at cost (600,000 and zero shares, respectively, at December 31, 2018 and 2017, respectively).	(42,543)	0
Retained earnings	769,575	723,062
Accumulated other comprehensive loss	(45,979)	(29,090)
TOTAL STOCKHOLDERS’ EQUITY	1,035,744	1,020,305
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	2,560,830	2,453,093
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