CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 219,452	$ 185,926
Accounts receivable [less allowance for doubtful accounts of $5,110 in 2018 and $5,427 in 2017]	281,523	246,188
Short-term investments	52,349	43,159
Prepaid expenses	32,790	32,206
Income tax receivable	13,281	11,339
Other current assets	2,299	1,997
Total current assets	601,694	520,815
Accounts receivable, long-term	12,966	12,107
Property and equipment, net	156,498	152,315
Other assets:
Goodwill	749,502	657,987
Other intangibles, net	282,806	229,617
Non-current investments and other assets	61,156	38,510
Total assets	1,864,622	1,611,351
Current liabilities:
Accounts payable	4,597	8,174
Accrued liabilities	66,020	64,675
Deferred revenue	326,421	298,613
Total current liabilities	397,038	371,462
Deferred revenue, long-term	493	1,274
Deferred income taxes	44,965	46,879
Commitments and contingencies
Shareholders' equity:
Preferred stock, $10.00 par value; 1,000,000 shares authorized; none issued	0	0
Common stock, $0.01 par value; 100,000,000 shares authorized; 48,147,969 shares issued and outstanding as of September 30, 2018 and December 31, 2017	481	481
Additional paid-in capital	724,935	626,867
Accumulated other comprehensive loss, net of tax	(46)	(46)
Retained earnings	740,373	624,463
Treasury stock, at cost; 9,179,922 and 10,262,182 shares in 2018 and 2017, respectively	(43,617)	(60,029)
Total shareholders' equity	1,422,126	1,191,736
Total liabilities and shareholders' equity	$ 1,864,622	$ 1,611,351