Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents at end of period	$ 1,115,130	$ 836,095
Short-term investments, available-for-sale	632,516	726,923
Accounts receivable, net of allowances of $4,645 and $5,883 at December 31, 2017 and 2016, respectively	712,535	681,206
Inventories, net	13,912	12,522
Prepaid expenses and other current assets	147,330	124,842
Current assets of discontinued operations	0	179,689
Total current assets	2,621,423	2,561,277
Long-term investments, available-for-sale	984,328	980,142
Property and equipment, net	252,932	261,954
Goodwill	1,614,494	1,585,893
Other intangible assets, net	141,952	173,681
Deferred tax assets, net	152,362	233,900
Other assets	52,685	54,449
Long-term assets of discontinued operations	0	538,931
Total assets	5,820,176	6,390,227
Current liabilities:
Accounts payable	66,893	72,724
Accrued expenses and other current liabilities	277,679	256,799
Income taxes payable	34,033	39,771
Current portion of deferred revenues	1,308,474	1,208,229
Convertible notes, short-term	0	1,348,156
Current liabilities of discontinued operations	0	172,670
Total current liabilities	1,687,079	3,098,349
Long-term portion of deferred revenues	555,769	476,135
Long-term debt	2,127,474	0
Long-term income taxes payable	335,457	0
Other liabilities	121,936	119,813
Long-term liabilities of discontinued operations	0	7,708
Commitments and contingencies
Temporary equity from Convertible notes	0	79,495
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; 305,751 and 302,851 shares issued and outstanding at December 31, 2017 and 2016, respectively	306	303
Additional paid-in capital	4,883,670	4,761,588
Retained earnings	3,509,484	4,010,737
Accumulated other comprehensive loss	(10,806)	(28,704)
Stockholders' equity before treasury stock	8,382,654	8,743,924
Less - common stock in treasury, at cost (162,044 and 146,552 shares at December 31, 2017 and 2016, respectively)	(7,390,193)	(6,135,197)
Total stockholders' equity	992,461	2,608,727
Total liabilities, temporary equity and stockholders' equity	$ 5,820,176	$ 6,390,227

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.