Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 134,279	$ 185,926
Accounts receivable (less allowance for losses of $4,647 in 2018 and $5,427 in 2017)	298,912	246,188
Short-term investments	44,306	43,159
Prepaid expenses	33,258	32,206
Income tax receivable	4,697	11,339
Other current assets	3,406	1,997
Total current assets	518,858	520,815
Accounts receivable, long-term	16,020	12,107
Property and equipment, net	155,177	152,315
Other assets:
Goodwill	753,718	657,987
Other intangibles, net	276,852	229,617
Non-current investments and other assets	70,338	38,510
Total assets	1,790,963	1,611,351
Current liabilities:
Accounts payable	6,910	8,174
Accrued liabilities	66,480	64,675
Deferred revenue	350,512	298,613
Total current liabilities	423,902	371,462
Revolving line of credit	0	0
Deferred revenue, long-term	424	1,274
Deferred income taxes	41,791	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 in 2018 and 2017	481	481
Additional paid-in capital	731,435	626,867
Accumulated other comprehensive loss, net of tax	(46)	(46)
Retained earnings	771,925	624,463
Treasury stock, at cost; 9,872,505 and 10,262,182 shares in 2018 and 2017, respectively	(178,949)	(60,029)
Total shareholders' equity	1,324,846	1,191,736
Liabilities and Shareholders' equity, Total	$ 1,790,963	$ 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).

Name:	us-gaap_AccountsPayableCurrent
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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682