CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 210,616	$ 185,926
Accounts receivable (less allowance for losses of $4,780 in 2018 and $5,427 in 2017)	216,516	246,188
Short-term investments	65,858	43,159
Prepaid expenses	30,262	32,206
Income tax receivable	7,286	11,339
Other current assets	2,098	1,997
Total current assets	532,636	520,815
Accounts receivable, long-term	11,550	12,107
Property and equipment, net	154,254	152,315
Other assets:
Goodwill	657,727	657,987
Other intangibles, net	221,069	229,617
Non-current investments and other assets	48,388	38,510
Total assets	1,625,624	1,611,351
Current liabilities:
Accounts payable	6,421	8,174
Accrued liabilities	44,996	64,675
Deferred revenue	268,132	298,613
Total current liabilities	319,549	371,462
Deferred revenue, long-term	641	1,274
Deferred income taxes	44,220	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 March 31, 2018 and December 31, 2017	481	481
Additional paid-in capital	652,909	626,867
Accumulated other comprehensive loss, net of tax	(46)	(46)
Retained earnings	662,288	624,463
Treasury stock, at cost; 9,900,041 and 10,262,182 shares in 2018 and 2017, respectively	(54,418)	(60,029)
Total shareholders' equity	1,261,214	1,191,736
Total liabilities and shareholders' equity	$ 1,625,624	$ 1,611,351

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.