Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 954,697	$ 1,115,130
Short-term investments, available-for-sale	510,267	632,516
Accounts receivable, net of allowances of $3,620 and $4,645 at March 31, 2018 and December 31, 2017, respectively	427,890	712,535
Inventories, net	13,569	13,912
Prepaid expenses and other current assets	168,987	147,330
Total current assets	2,075,410	2,621,423
Long-term investments, available-for-sale	773,654	984,328
Property and equipment, net	249,696	252,932
Goodwill	1,662,568	1,614,494
Other intangible assets, net	155,895	141,952
Deferred tax assets, net	114,277	152,362
Other assets	105,977	52,685
Total assets	5,137,477	5,820,176
Current liabilities:
Accounts payable	68,702	66,893
Accrued expenses and other current liabilities	243,940	277,679
Income taxes payable	4,818	34,033
Current portion of deferred revenues	1,204,199	1,308,474
Total current liabilities	1,521,659	1,687,079
Long-term portion of deferred revenues	480,985	555,769
Long-term debt	2,137,418	2,127,474
Long-term income taxes payable	335,457	335,457
Other liabilities	138,580	121,936
Commitments and contingencies
Stockholders' equity:
Preferred stock at $.01 par value: 5,000 shares authorized, none issued and outstanding	0	0
Common stock at $.001 par value: 1,000,000 shares authorized; 307,575 and 305,751 shares issued and outstanding at March 31, 2018 and December 31, 2017, respectively	308	306
Additional paid-in capital	4,938,533	4,883,670
Retained earnings	3,786,521	3,509,484
Accumulated other comprehensive loss	(14,874)	(10,806)
Stockholders' equity before treasury stock	8,710,488	8,382,654
Less - common stock in treasury, at cost (170,431 and 162,044 shares at March 31, 2018 and December 31, 2017, respectively)	(8,187,110)	(7,390,193)
Total stockholders' equity	523,378	992,461
Total liabilities and stockholders' equity	$ 5,137,477	$ 5,820,176

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.