Citrix Systems (CTXS) 10-K 15 Feb 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information Document - USD ($)	12 Months Ended
	Dec. 31, 2018	Feb. 08, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Trading Symbol	ctxs
Entity Registrant Name	CITRIX SYSTEMS INC
Entity Central Index Key	877,890
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		131,725,833
Entity Well-known Seasoned Issuer	Yes
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 13,765,749,900

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 618,766	$ 1,115,130
Short-term investments, available-for-sale	583,615	632,516
Accounts receivable, net of allowances of $4,530 and $4,645 at December 31, 2018 and 2017, respectively	688,420	712,535
Inventories, net	21,905	13,912
Prepaid expenses and other current assets	174,195	147,330
Total current assets	2,086,901	2,621,423
Long-term investments, available-for-sale	574,319	984,328
Property and equipment, net	243,396	252,932
Goodwill	1,802,670	1,614,494
Other intangible assets, net	167,187	141,952
Deferred tax assets, net	136,998	152,362
Other assets	124,578	52,685
Total assets	5,136,049	5,820,176
Current liabilities:
Accounts payable	75,551	66,893
Accrued expenses and other current liabilities	290,492	277,679
Income taxes payable	44,409	34,033
Current portion of deferred revenues	1,345,243	1,308,474
Convertible notes, short-term	1,155,445	0
Total current liabilities	2,911,140	1,687,079
Long-term portion of deferred revenues	489,329	555,769
Long-term debt	741,825	2,127,474
Long-term income taxes payable	285,627	335,457
Other liabilities	148,499	121,936
Commitments and contingencies
Temporary equity from Convertible notes	8,110	0
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; 309,761 and 305,751 shares issued and outstanding at December 31, 2018 and 2017, respectively	310	306
Additional paid-in capital	5,404,500	4,883,670
Retained earnings	4,169,019	3,509,484
Accumulated other comprehensive loss	(8,154)	(10,806)
Stockholders' equity before treasury stock	9,565,675	8,382,654
Less - common stock in treasury, at cost (178,327 and 162,044 shares at December 31, 2018 and 2017, respectively)	(9,014,156)	(7,390,193)
Total stockholders' equity	551,519	992,461
Total liabilities, temporary equity and stockholders' equity	$ 5,136,049	$ 5,820,176

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accounts receivable, allowances	$ 4,530	$ 4,645
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	309,761,000	305,751,000
Common stock, shares outstanding	309,761,000	305,751,000
Common stock in treasury, at cost	178,327,000	162,044,000

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Revenues:
Revenues	$ 2,973,903	$ 2,824,686	[1],[2]	$ 2,736,080	[1],[2]
Cost of net revenues:
Amortization and impairment of intangible assets	62,913	82,878		70,494
Total cost of net revenues	433,803	439,646		404,889
Gross margin	2,540,100	2,385,040		2,331,191
Operating expenses:
Research and development	439,984	415,801		395,373
Sales, marketing and services	1,074,234	1,006,112		976,339
General and administrative	315,343	302,565		316,838
Amortization and impairment of other intangible assets	15,854	17,190		15,076
Restructuring	16,725	72,375		67,401
Total operating expenses	1,862,140	1,814,043		1,771,027
Income from continuing operations	677,960	570,997		560,164
Interest income	40,030	27,808		16,686
Interest expense	(80,162)	(51,609)		(44,949)
Other (expense) income, net	(8,373)	3,150		(4,131)
Income from continuing operations before income taxes	629,455	550,346		527,770
Income tax expense	53,788	528,361		57,915
Income from continuing operations	575,667	21,985		469,855
(Loss) income from discontinued operations, net of income tax expense of $2,900 and $22,737 in 2017 and 2016, respectively	0	(42,704)		66,257
Net income (loss)	$ 575,667	$ (20,719)		$ 536,112
Basic earnings (loss) per share:
Income from continuing operations (USD per share)	$ 4.23	$ 0.15		$ 3.03
(Loss) income from discontinued operations (USD per share)	0	(0.28)		0.43
Basic net earnings (loss) per share (USD per share)	4.23	(0.13)		3.46
Diluted earnings (loss) per share:
Income from continuing operations (USD per share)	3.94	0.14		2.99
(Loss) income from discontinued operations (USD per share)	0	(0.27)		0.42
Diluted net earnings (loss) per share (USD per share)	$ 3.94	$ (0.13)		$ 3.41
Weighted average shares outstanding:
Basic (in shares)	136,030	150,779		155,134
Diluted (in shares)	145,934	155,503		157,084
Subscription
Revenues:
Revenues	$ 455,276	$ 314,735		$ 245,606
Product and license
Revenues:
Revenues	734,495	766,777		810,975
Cost of net revenues:
Cost of services and maintenance revenues	120,249	123,356		121,391
Support and services
Revenues:
Revenues	1,784,132	1,743,174		1,679,499
Cost of subscription, support and services
Cost of net revenues:
Cost of services and maintenance revenues	266,495	250,602		228,080
Product related intangible assets
Cost of net revenues:
Amortization and impairment of intangible assets	$ 47,059	$ 65,688		$ 55,418
[1]	As noted above, prior period amounts have not been adjusted under the modified retrospective method of adoption of therevenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenuerecognition standard.
[2]	Prior period amounts have not been adjusted under the modified retrospective method of adoption of the revenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenue recognition standard.

Consolidated Statements of In_2

Consolidated Statements of Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
(Loss) income from discontinued operations, tax	$ 0	$ 2,900	$ 22,737

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 575,667	$ (20,719)	$ 536,112
Available for sale securities:
Change in net unrealized (losses) gains	(1,770)	(3,285)	996
Less: reclassification adjustment for net losses (gains) included in net income	5,996	(273)	(1,204)
Net change (net of tax effect)	4,226	(3,558)	(208)
Gain on pension liability	1,569	2,768	906
Cash flow hedges:
Change in unrealized (losses) gains	(3,842)	6,046	(2,638)
Less: reclassification adjustment for net losses (gains) included in net income	699	(758)	1,763
Net change (net of tax effect)	(3,143)	5,288	(875)
Other comprehensive income (loss)	2,652	4,498	(177)
Comprehensive income (loss)	$ 578,319	$ (16,221)	$ 535,935

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid In Capital	Retained Earnings	Accumulated Other Comprehensive (loss) income	Common Stock in Treasury
Beginning balance (in shares) at Dec. 31, 2015		299,113,000
Beginning balance at Dec. 31, 2015	$ 1,973,446	$ 299	$ 4,566,919	$ 3,474,625	$ (28,527)	$ (6,039,870)
Beginning balance, treasury shares (in shares) at Dec. 31, 2015						(145,296,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under stock-based compensation plans	41,247	$ 3	41,244
Shares issued under stock-based compensation plans (in shares)		3,009,000
Stock-based compensation expense	175,980		175,980
Common stock issued under employee stock purchase plan	57,515	$ 1	57,514
Common stock issued under employee stock purchase plan (in shares)		729,000
Temporary equity reclassification	(79,495)		(79,495)
Stock repurchases, net	(28,689)					$ (28,689)
Stock repurchases, net (in shares)						(426,000)
Tax deficiency from employer stock plans, net	(574)		(574)
Restricted shares turned in for tax withholding	$ (66,638)					$ (66,638)
Restricted shares turned in for tax withholding (in shares)	(830,155)					(830,000)
Other comprehensive income (loss), net of tax	$ (177)				(177)
Net income (loss)	536,112			536,112
Ending balance (in shares) at Dec. 31, 2016		302,851,000
Ending balance at Dec. 31, 2016	2,608,727	$ 303	4,761,588	4,010,737	(28,704)	$ (6,135,197)
Ending balance, treasury shares (in shares) at Dec. 31, 2016						(146,552,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under stock-based compensation plans	2,113	$ 3	2,110
Shares issued under stock-based compensation plans (in shares)		2,614,000
Stock-based compensation expense	166,308		166,308
Common stock issued under employee stock purchase plan	19,326		19,326
Common stock issued under employee stock purchase plan (in shares)		286,000
Temporary equity reclassification	79,495		79,495
Stock repurchases, net	(574,956)					$ (574,956)
Stock repurchases, net (in shares)						(7,384,000)
Accelerated stock repurchase program	(750,000)		(150,000)			$ (600,000)
Accelerated stock repurchase program (shares)						(7,133,000)
Restricted shares turned in for tax withholding	$ (80,040)					$ (80,040)
Restricted shares turned in for tax withholding (in shares)	(974,501)					(975,000)
Cumulative-effect adjustment from adoption of accounting standards	$ 388		5,691	(5,303)
Distribution of the net assets of the GoTo Business	(461,831)			(475,231)	13,400
Other	(848)		(848)
Other comprehensive income (loss), net of tax	4,498				4,498
Net income (loss)	(20,719)			(20,719)
Ending balance (in shares) at Dec. 31, 2017		305,751,000
Ending balance at Dec. 31, 2017	$ 992,461	$ 306	4,883,670	3,509,484	(10,806)	$ (7,390,193)
Ending balance, treasury shares (in shares) at Dec. 31, 2017	(162,044,000)					(162,044,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under stock-based compensation plans	$ 164	$ 3	161
Shares issued under stock-based compensation plans (in shares)		2,258,000
Stock-based compensation expense	203,619		203,619
Common stock issued under employee stock purchase plan	33,462		33,462
Common stock issued under employee stock purchase plan (in shares)		461,000
Temporary equity reclassification	(8,110)		(8,110)
Stock repurchases, net	(511,153)					$ (511,153)
Stock repurchases, net (in shares)						(4,731,000)
Accelerated stock repurchase program	(750,000)		150,000			$ (900,000)
Accelerated stock repurchase program (shares)						(9,522,000)
Restricted shares turned in for tax withholding	$ (71,593)					$ (71,593)
Restricted shares turned in for tax withholding (in shares)	(739,522)					(739,000)
Cash dividends declared	$ (46,799)			(46,799)
Settlement of convertible notes and hedges		$ 1	138,231
Settlement of convertible notes and hedges	(2,985)					$ (141,217)
Settlement of convertible notes and hedges (shares)		1,291,000
Settlement of convertible notes and hedges (shares)						1,291,000
Cumulative-effect adjustment from adoption of accounting standards	132,778			132,778
Other	1,356		3,467	(2,111)
Other comprehensive income (loss), net of tax	2,652				2,652
Net income (loss)	575,667			575,667
Ending balance (in shares) at Dec. 31, 2018		309,761,000
Ending balance at Dec. 31, 2018	$ 551,519	$ 310	$ 5,404,500	$ 4,169,019	$ (8,154)	$ (9,014,156)
Ending balance, treasury shares (in shares) at Dec. 31, 2018	(178,327,000)					(178,327,000)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Operating Activities
Net income (loss)	$ 575,667	$ (20,719)	$ 536,112
Loss (income) from discontinued operations	0	42,704	(66,257)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Amortization and impairment of intangible assets	62,913	82,878	70,494
Depreciation and amortization of property and equipment	78,983	87,137	107,954
Amortization of debt discount and transaction costs	39,099	38,298	37,085
Amortization of deferred costs	38,144	0	0
Stock-based compensation expense	203,619	165,120	152,739
Deferred income tax (benefit) expense	(13,156)	94,158	(21,654)
Excess tax benefit from stock-based compensation			(16,049)
Effects of exchange rate changes on monetary assets and liabilities denominated in foreign currencies	7,950	(7,645)	5,189
Other non-cash items	11,872	11,924	8,618
Total adjustments to reconcile net income (loss) to net cash provided by operating activities	429,424	471,870	344,376
Changes in operating assets and liabilities, net of the effects of acquisitions:
Accounts receivable	18,703	(33,904)	(61,662)
Inventories	(8,239)	(2,545)	(4,133)
Prepaid expenses and other current assets	(7,855)	(18,327)	(12,077)
Other assets	(33,638)	2,116	(2,747)
Income taxes, net	(56,988)	318,795	42,431
Accounts payable	6,804	(7,238)	(16,365)
Accrued expenses and other current liabilities	36,967	34,886	22,650
Deferred revenues	69,499	174,426	142,381
Other liabilities	5,001	2,282	22,459
Total changes in operating assets and liabilities, net of the effects of acquisitions	30,254	470,491	132,937
Net cash provided by operating activities of continuing operations	1,035,345	964,346	947,168
Net cash (used in) provided by operating activities of discontinued operations	0	(56,070)	168,662
Net cash provided by operating activities	1,035,345	908,276	1,115,830
Investing Activities
Purchases of available-for-sale investments	(466,687)	(1,155,659)	(2,238,784)
Proceeds from sales of available-for-sale investments	455,417	775,135	1,294,636
Proceeds from maturities of available-for-sale investments	468,145	466,900	632,517
Purchases of property and equipment	(69,354)	(80,901)	(85,035)
Cash paid for acquisitions, net of cash acquired	(248,929)	(60,449)	(13,242)
Cash paid for licensing agreements and product related intangible assets	(3,210)	(7,379)	(25,940)
Other	(3,202)	2,323	1,181
Net cash provided by (used in) investing activities of continuing operations	132,180	(60,030)	(434,667)
Net cash used in investing activities of discontinued operations	0	(3,891)	(49,537)
Net cash provided by (used in) investing activities	132,180	(63,921)	(484,204)
Financing Activities
Proceeds from issuance of common stock under stock-based compensation plans	164	2,114	41,247
Proceeds from revolving credit facility	0	165,000	0
Repayments on credit facility	0	(165,000)	0
Proceeds from 2027 notes, net of issuance costs	0	741,039	0
Repayment of acquired debt	(5,674)	(4,000)	0
Excess tax benefit from stock-based compensation			16,049
Stock repurchases, net	(1,261,153)	(1,174,957)	(28,689)
Accelerated stock repurchase program	0	(150,000)	0
Cash paid for tax withholding on vested stock awards	(71,593)	(80,040)	(66,638)
Common stock cash dividends paid	(46,799)	0	0
Repayment on convertible debt	(272,986)	0	0
Transfer of cash to GoTo Business resulting from the separation	0	(28,523)	0
Net cash used in financing activities	(1,658,041)	(694,367)	(38,031)
Effect of exchange rate changes on cash and cash equivalents	(5,848)	8,186	(5,157)
Change in cash and cash equivalents	(496,364)	158,174	588,438
Cash and cash equivalents at beginning of period, including cash of discontinued operations of $0, $120,861 and $57,762, respectively	1,115,130	956,956	368,518
Cash and cash equivalents at end of period	618,766	1,115,130	956,956
Less cash of discontinued operations	0	0	(120,861)
Cash and cash equivalents at end of period	618,766	1,115,130	836,095
Supplemental Cash Flow Information
Cash paid for income taxes	110,808	61,126	64,361
Cash paid for interest	$ 41,834	$ 8,764	$ 7,847

Background and Organization

Background and Organization	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BACKGROUND AND ORGANIZATION	BACKGROUND AND ORGANIZATION Citrix Systems, Inc. ("Citrix" or the "Company"), is a Delaware corporation incorporated on April 17, 1989. Citrix aims to power a better way to work by delivering the experience, security, and choice people and organizations need to unlock innovation, engage customers, and be productive - anytime, anywhere. Citrix markets and licenses its solutions through multiple channels worldwide, including selling through resellers, direct and over the Web. Citrix's partner community comprises thousands of value-added resellers, or VARs known as Citrix Solution Advisors, value-added distributors, or VADs, systems integrators, or SIs, independent software vendors, or ISVs, original equipment manufacturers, or OEMs and Citrix Service Providers, or CSPs. The Company's revenues are derived from sales of its Digital Workspace solutions (formerly Workspace Services and Content Collaboration), Networking products and related Support and services. The Company operates under one reportable segment. The Company's chief operating decision maker (“CODM”) reviews financial information presented on a consolidated basis for purposes of allocating resources and evaluating financial performance. See Note 12 for more information on the Company's segment. On January 31, 2017, the Company completed the spin-off of its GoTo family of service offerings (the “Spin-off”) and subsequent merger of that business with LogMeIn, Inc. pursuant to a pro rata distribution to its stockholders of 100% of the shares of common stock of GetGo, Inc., or GetGo, its wholly-owned subsidiary. In these consolidated financial statements, unless otherwise indicated, references to Citrix and the Company, refer to Citrix Systems, Inc. and its consolidated subsidiaries after giving effect to the Spin-off. As a result of the Spin-off, the consolidated financial statements reflect the GoTo Business operations, assets and liabilities, and cash flows as discontinued operations for all periods presented. Refer to Note 3 for additional information regarding discontinued operations.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
SIGNIFICANT ACCOUNTING POLICIES	SIGNIFICANT ACCOUNTING POLICIES Consolidation Policy The consolidated financial statements of the Company include the accounts of its wholly-owned subsidiaries in the Americas; Europe, the Middle East and Africa (“EMEA”); and Asia-Pacific and Japan ("APJ"). All significant transactions and balances between the Company and its subsidiaries have been eliminated in consolidation. Recent Accounting Pronouncements Revenue Recognition In May 2014, the Financial Accounting Standards Board issued an accounting standard update ("ASC 606") on revenue recognition. The new guidance creates a single, principle-based model for revenue recognition that expands and improves disclosures about revenue. On January 1, 2018, the Company adopted the accounting standard update for revenue from contracts with customers on a modified retrospective basis, applying the practical expedient to all contracts that the Company had not completed as of January 1, 2018. The Company elected the modified retrospective method of adoption; and consequently, results for reporting periods beginning after January 1, 2018 are presented under the new revenue standard, while prior period amounts are not adjusted and continue to be reported under the revenue accounting literature in effect during those periods. The Company recorded a net increase to retained earnings of $130.7 million as of January 1, 2018 as a result of the transition, with the impact primarily related to the cumulative effect of a decrease in deferred revenue from the upfront recognition of term licenses and the general requirement to allocate the transaction price on a relative stand-alone selling price of $99.9 million , and an increase in contract assets of $7.3 million , the cumulative effect of a decrease in commission expense of $66.4 million , partially offset by an increase from the cumulative effect of the impact on deferred income taxes of $42.9 million . The impact of adoption of ASC 606 to the Company’s consolidated statements of income and balance sheets are as follows: Year Ended December 31, 2018 As Reported Balances without adoption of ASC 606 Effect of Change Higher/(Lower) (in thousands, except per share amounts) Total net revenues $ 2,973,903 $ 2,966,848 $ 7,055 Total cost of net revenues 433,803 431,974 1,829 Gross profit 2,540,100 2,534,874 5,226 Total operating expenses 1,862,140 1,890,692 (28,552 ) Income from operations 677,960 644,182 33,778 Net income $ 575,667 $ 548,430 $ 27,237 Basic earnings per share $ 4.23 $ 4.03 $ 0.20 Diluted earnings per share $ 3.94 $ 3.76 $ 0.18 As of December 31, 2018 As Reported Balances without adoption of ASC 606 Effect of Change Higher/(Lower) (in thousands) Prepaid expenses and other current assets (1) $ 174,195 $ 147,554 $ 26,641 Other assets (2) 124,578 52,732 71,846 Deferred tax assets, net 136,998 169,064 (32,066 ) Total assets $ 5,136,049 $ 5,069,628 $ 66,421 Other liabilities (3) 148,499 135,430 13,069 Current portion of deferred revenues 1,345,243 1,413,839 (68,596 ) Long-term portion of deferred revenues 489,329 526,763 (37,434 ) Total liabilities $ 4,576,420 $ 4,669,381 $ (92,961 ) Stockholders' Equity: Retained earnings $ 4,169,019 $ 4,009,637 $ 159,382 (1) As reported primarily includes contract acquisition costs of $41.0 million . The balance without adoption of ASC 606 includes contract acquisition costs of $14.2 million . (2) As reported primarily includes contract acquisition costs of $68.2 million . (3) As reported includes deferred tax liabilities of $54.7 million . The balance without adoption of ASC 606 includes deferred tax liabilities of $56.6 million . Adoption of the standard had no impact to cash from or used in operating, financing, or investing activities on the Company’s consolidated cash flows statements. Accounting for Business Combinations In January 2017, the Financial Accounting Standards Board issued an accounting standard update on the accounting for business combinations by clarifying the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions or disposals of assets or businesses. The Company adopted the standard effective January 1, 2018. The adoption of this standard had no impact on the Company's consolidated financial position, results of operations and cash flows. Accounting for Income Taxes In October 2016, the Financial Accounting Standards Board issued an accounting standard update on the accounting for income taxes, which requires entities to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transaction occurs as opposed to deferring tax consequences and amortizing them into future periods. A modified retrospective approach with a cumulative-effect adjustment directly to retained earnings at the beginning of the period of adoption is required. The Company adopted the standard effective January 1, 2018. The adoption of this standard did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. Accounting for Investments In January 2016, the Financial Accounting Standards Board issued an accounting standard update for the recognition and measurement of financial assets and liabilities. Under the standard, equity investments that do not have readily determinable fair values and do not qualify for the net asset value practical expedient are eligible for the measurement alternative. For the Company’s equity investments in private equity securities, which do not have readily determinable fair values, the Company has elected the measurement alternative defined as cost, less impairment, plus or minus adjustments resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. For certain of the Company’s equity investments in private equity funds, the Company has elected to use the net asset value practical expedient. The guidance of this accounting standard update was adopted effective January 1, 2018. The impact of adopting the accounting standard update was not material to the consolidated financial statements. In February 2018, the Financial Accounting Standards Board issued an accounting standard update that clarified and amended some of the updates made in the January 2016 update to the recognition and measurement of financial assets and liabilities. The Company has elected to early adopt this accounting standard update effective January 1, 2018. The impact of adopting the accounting standard update was not material to the consolidated financial statements. Leases In February 2016, the Financial Accounting Standards Board issued an accounting standard update on the accounting for leases. The new guidance requires that lessees in a leasing arrangement recognize a right-of-use asset and a lease liability for most leases (other than leases that meet the definition of a short-term lease). The liability will be equal to the present value of lease payments. The asset will be based on the liability, subject to adjustment, such as for initial direct costs. The new guidance is effective for annual reporting periods beginning after December 15, 2018. Under the original guidance, the modified retrospective method of adoption was mandatory, and would have required application of the standard at the beginning of the earliest comparative period presented. However, in July 2018, the Financial Accounting Standards Board issued an update which permits entities to adopt the standard using another transition method. Under this optional transition method, the Company would recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. The Company adopted this standard effective January 1, 2019, using the optional transition method. The Company has concluded an assessment of its systems, data and processes related to the implementation of this accounting standard and has substantially completed its information technology system design and solution development. Adoption of the standard is expected to result in the recognition of additional right-of-use assets and lease liabilities for operating leases (net of previously recorded lease losses related to the consolidated leased facilities) in the range of $200.0 million to $250.0 million . The Company does not expect a material impact to its results of operations. Accounting for Cloud Computing Costs In August 2018, the Financial Accounting Standards Board issued an accounting standard update on the accounting for implementation costs incurred by customers in cloud computing arrangements that are service contracts. The new guidance aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The new guidance is effective for annual reporting periods beginning after December 15, 2019, and interim periods within those fiscal years, and early adoption is permitted. The standard can be adopted either using the prospective or retrospective transition approach. The Company will early adopt this standard on January 1, 2019 and does not expect a material impact from adoption on its consolidated financial position and results of operations. Fair Value Measurements In August 2018, the Financial Accounting Standards Board issued an accounting standard update on fair value measurements. The new guidance modifies the disclosure requirements on fair value measurements by removing certain disclosure requirements related to the fair value hierarchy, modifying existing disclosure requirements related to measurement uncertainty, and adding new disclosure requirements. The new guidance is effective for annual reporting periods beginning after December 15, 2019, and interim periods within those fiscal years, and early adoption is permitted. The adoption of this standard is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Reclassifications Certain reclassifications of the prior years' amounts have been made to conform to the current year's presentation. Beginning in the first quarter of fiscal year 2018, the Company revised its presentation of revenue to align with its transition to a subscription business model as follows: (1) subscription revenue, which includes revenue from the Company's cloud services offerings and on-premise subscriptions as well as revenue from its Citrix Service Provider ("CSP") offerings; (2) product and license revenue from perpetual product and license offerings; and (3) support and services revenue for perpetual product and license offerings. This change in manner of presentation did not affect the Company's total net revenues, total cost of net revenues or gross margin. Conforming changes have been made for all periods presented, as follows (in thousands): Year Ended December 31, 2017 As Previously Reported Amount Reclassified As Reported Revenues: Revenues: Software as a service $ 175,762 $ 138,973 Subscription $ 314,735 Product and licenses (1) 857,253 (90,476 ) Product and license 766,777 License updates and maintenance (2) 1,659,936 83,238 Support and services (3) 1,743,174 Professional services 131,735 (131,735 ) Total net revenues $ 2,824,686 $ — Total net revenues $ 2,824,686 Year Ended December 31, 2016 As Previously Reported Amount Reclassified As Reported Revenues: Revenues: Software as a service $ 134,682 $ 110,924 Subscription $ 245,606 Product and licenses (1) 882,898 (71,923 ) Product and license 810,975 License updates and maintenance (2) 1,587,271 92,228 Support and services (3) 1,679,499 Professional services 131,229 (131,229 ) Total net revenues $ 2,736,080 $ — Total net revenues $ 2,736,080 (1) Product and licenses as previously reported included revenue from CSPs and on-premise subscriptions that are now included in Subscription. Current period presentation only includes revenues from perpetual offerings and hardware. (2) License updates and maintenance as previously reported included revenue from CSPs and on-premise license updates and maintenance that are now included in Subscription. (3) Support and services includes revenues from license updates and maintenance from perpetual offerings as well as professional services. Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Significant estimates made by management include the standalone selling price related to revenue recognition, the provision for doubtful accounts receivable, the provision to reduce obsolete or excess inventory to market, the provision for estimated returns, as well as sales allowances, the assumptions used in the valuation of stock-based awards, the assumptions used in the discounted cash flows to mark certain of its investments to market, the valuation of the Company’s goodwill, net realizable value of product related and other intangible assets, the provision for lease losses, the provision for income taxes, valuation allowance for deferred tax assets, uncertain tax positions, and the amortization and depreciation periods for contract acquisition costs, intangible and long-lived assets. While the Company believes that such estimates are fair when considered in conjunction with the consolidated financial position and results of operations taken as a whole, the actual amounts of such items, when known, will vary from these estimates. Cash and Cash Equivalents Cash and cash equivalents at December 31, 2018 and 2017 include marketable securities, which are primarily money market funds, commercial paper, agency, and government securities, municipal securities and corporate securities with initial or remaining contractual maturities when purchased of three months or less. Available-for-sale Investments Short-term and long-term available for sale investments at December 31, 2018 and 2017 primarily consist of agency securities, corporate securities, municipal securities and government securities. Investments classified as available-for-sale are stated at fair value with unrealized gains and losses, net of taxes, reported in Accumulated other comprehensive loss. The Company classifies its available-for-sale investments as current and non-current based on their actual remaining time to maturity. The Company does not recognize changes in the fair value of its available-for-sale investments in income unless a decline in value is considered other-than-temporary in accordance with the authoritative guidance. The Company’s investment policy is designed to limit exposure to any one issuer depending on credit quality. The Company uses information provided by third parties to adjust the carrying value of certain of its investments to fair value at the end of each period. Fair values are based on a variety of inputs and may include interest rates, known historical trades, yield curve information, benchmark data, prepayment speeds, credit quality and broker/dealer quotes. See Note 5 for investment information. Accounts Receivable The Company’s accounts receivable are attributable primarily to direct sales to end customers via the Web and through value-added resellers, or VARs known as Citrix Solution Advisors, value-added distributors, or VADs, systems integrators, or SIs, independent software vendors, or ISVs, original equipment manufacturers, or OEMs and Citrix Service Providers, or CSPs. Collateral is generally not required. The Company also maintains allowances for doubtful accounts for estimated losses resulting from the inability of the Company’s customers to make payments which includes both general and specific reserves. The Company periodically reviews these estimated allowances by conducting an analysis of the customer's payment history and credit worthiness, the age of the trade receivable balances and current economic conditions that may affect a customer’s ability to make payments. Based on this review, the Company specifically reserves for those accounts deemed uncollectible. When receivables are determined to be uncollectible, principal amounts of such receivables outstanding are deducted from the allowance. The allowance for doubtful accounts was $3.6 million and $3.4 million as of December 31, 2018 and 2017 , respectively. If the financial condition of a significant customer were to deteriorate, the Company’s operating results could be adversely affected. As of December 31, 2018 , one distributor, the Arrow Group, accounted for 17% of gross accounts receivable. At December 31, 2017 , one distributor, the Arrow Group, accounted for 14% of gross accounts receivable. Inventory Inventories are stated at the lower of cost or net realizable value on a standard cost basis, which approximates actual cost. The Company’s inventories primarily consist of finished goods as of December 31, 2018 and 2017 . Contract acquisition costs In conjunction with the adoption of the new revenue recognition standard, the Company is required to capitalize certain contract acquisition costs consisting primarily of commissions paid and related payroll taxes when contracts are signed. The asset recognized from capitalized incremental and recoverable acquisition costs is amortized on a basis consistent with the pattern of transfer of the products or services to which the asset relates and is recognized in Prepaid expenses and other current assets and Other assets in the accompanying consolidated balance sheets. The Company’s typical contracts include performance obligations related to product and licenses and support. In these contracts, incremental costs of obtaining a contract are allocated to the performance obligations based on the relative estimated standalone selling prices and then recognized on a basis that is consistent with the transfer of the goods or services to which the asset relates. The commissions paid on annual renewals of support for product and licenses are not commensurate with the initial commission. The costs allocated to product and licenses are expensed at the time of sale, when revenue for the product and functional software licenses is recognized. The costs allocated to customer support for product and licenses are amortized ratably over a period of the greater of the contract term or the average customer life, the expected period of benefit of the asset capitalized. The Company currently estimates an average customer life of two to five years, which it believes is appropriate based on consideration of the historical average customer life and the estimated useful life of the underlying product and license sold as part of the transaction. Amortization of contract acquisition costs related to support are limited to the contractual period of the arrangement as the Company intends to pay a commensurate commission upon renewal of the related support. For contracts that contain multi-year services or subscriptions, the amortization period of the capitalized costs is the expected period of benefit, which is the greater of the contractual term or the expected customer life. The Company elects to apply a practical expedient to expense contract acquisition costs as incurred where the expected period of benefit is one year or less. For the year ended on December 31, 2018, the Company recorded amortization costs of $38.1 million in relation to costs capitalized during the year, which are recorded in Sales, Marketing and Services expense in the accompanying consolidated statements of income. There was no impairment loss in relation to costs capitalized during the year ended on December 31, 2018. Derivatives and Hedging Activities In accordance with the authoritative guidance, the Company records derivatives at fair value as either assets or liabilities on the balance sheet. For derivatives that are designated as and qualify as effective cash flow hedges, the portion of gain or loss on the derivative instrument effective at offsetting changes in the hedged item is reported as a component of Accumulated other comprehensive loss and reclassified into earnings as operating expense, net, when the hedged transaction affects earnings. Derivatives not designated as hedging instruments are adjusted to fair value through earnings as Other (expense) income, net , in the period during which changes in fair value occur. The application of the authoritative guidance could impact the volatility of earnings. The Company formally documents all relationships between hedging instruments and hedged items, as well as its risk-management objective and strategy for undertaking various hedge transactions. This process includes attributing all derivatives that are designated as cash flow hedges to floating rate assets or liabilities or forecasted transactions. The Company also formally assesses, both at the inception of the hedge and on an ongoing basis, whether each derivative is highly effective in offsetting changes in cash flows of the hedged item. Fluctuations in the value of the derivative instruments are generally offset by changes in the hedged item; however, if it is determined that a derivative is not highly effective as a hedge or if a derivative ceases to be a highly effective hedge, the Company will discontinue hedge accounting prospectively for the affected derivative. The Company is exposed to risk of default by its hedging counterparties. Although this risk is concentrated among a limited number of counterparties, the Company’s foreign exchange hedging policy attempts to minimize this risk by placing limits on the amount of exposure that may exist with any single financial institution at a time. Property and Equipment Property and equipment is stated at cost. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, which is generally three years for computer equipment and software; the lesser of the lease term or ten years for leasehold improvements, which is the estimated useful life; seven years for office equipment and furniture and the Company’s enterprise resource planning systems; and 40 years for buildings. During 2018 and 2017 , the Company retired $13.4 million and $16.9 million , respectively, in property and equipment that were no longer in use. At the time of retirement, the remaining net book value of the assets retired was not material and no material asset retirement obligations were associated with them. Property and equipment consist of the following: December 31, 2018 2017 (In thousands) Buildings $ 76,152 $ 76,152 Computer equipment 189,333 176,140 Software 433,033 388,583 Equipment and furniture 78,401 73,700 Leasehold improvements 182,848 168,656 959,767 883,231 Less: accumulated depreciation and amortization (741,587 ) (675,892 ) Assets under construction 8,447 28,824 Land 16,769 16,769 Total $ 243,396 $ 252,932 Long-Lived Assets The Company reviews for impairment of long-lived assets and certain identifiable intangible assets to be held and used whenever events or changes in circumstances indicate that the carrying amount of such assets may not be fully recoverable. Determination of recoverability is based on an estimate of undiscounted future cash flows resulting from the use of the asset and its eventual disposition. Measurement of an impairment loss is based on the fair value of the asset compared to its carrying value. Long-lived assets and certain identifiable intangible assets to be disposed of are reported at the lower of carrying amount or fair value less costs to sell. Goodwill The Company accounts for goodwill in accordance with the authoritative guidance, which requires that goodwill and certain intangible assets are not amortized, but are subject to an annual impairment test. During 2018, the Company initiated an effort to streamline and simplify its product branding and packaging, which included naming updates to the portfolio to provide clarity on the Company's offerings and unify its sales motions. The change resulted in the Company consolidating its Content Collaboration product group with Workspace Services and renaming the new product group Digital Workspace. As a result, the Company's two reporting units (Enterprise and Service Provider and Content Collaboration) were combined into one , consistent with how management reviews the operating results of the business. In connection with this change, the Company performed a qualitative goodwill assessment of the reporting units and determined there were no indicators of impairment during the third quarter of 2018. The change in reporting units did not result in a reallocation of goodwill or a change in reportable segments. In addition, there was no impairment of goodwill or indefinite lived intangible assets as a result of the annual impairment analysis completed during the fourth quarters of 2018 and 2017. See Note 4 for more information regarding the Company's acquisitions and Note 12 for more information regarding the Company's segments. The following table presents the change in goodwill during 2018 and 2017 (in thousands): Balance at January 1, 2018 Additions Other Balance at December 31, 2018 Balance at January 1, 2017 Additions Other Balance at December 31, 2017 Goodwill $ 1,614,494 $ 188,176 (1) $ — $ 1,802,670 $ 1,585,893 $ 28,601 (2) $ — $ 1,614,494 (1) Amount relates to preliminary purchase price allocation of goodwill associated with the 2018 business combinations. See Note 4 for more information regarding the Company's acquisitions. (2) Amount relates to the purchase price allocation of goodwill associated with the 2017 business combination. See Note 4 for more information regarding the Company's acquisitions. Intangible Assets The Company has intangible assets which were primarily acquired in conjunction with business combinations and technology purchases. Intangible assets with finite lives are recorded at cost, less accumulated amortization. Amortization is computed over the estimated useful lives of the respective assets, generally three to seven years, except for patents, which are amortized over the lesser of their remaining life or ten years. In-process R&D is initially capitalized at fair value as an intangible asset with an indefinite life and assessed for impairment thereafter. When in-process R&D projects are completed, the corresponding amount is reclassified as an amortizable intangible asset and is amortized over the asset's estimated useful life. Intangible assets consist of the following (in thousands): December 31, 2018 Gross Carrying Amount Accumulated Amortization Weighted-Average Life (Years) Product related intangible assets $ 746,152 $ 601,993 6.06 Other 227,922 204,894 6.40 Total $ 974,074 $ 806,887 6.14 December 31, 2017 Gross Carrying Amount Accumulated Amortization Weighted-Average Life (Years) Product related intangible assets $ 663,004 $ 554,934 6.10 Other 222,923 189,041 6.49 Total $ 885,927 $ 743,975 6.20 Amortization and impairment of product related intangible assets, which consists primarily of product-related technologies and patents, was $47.1 million and $65.7 million for the year ended December 31, 2018 and 2017 , respectively, and is classified as a component of Cost of net revenues in the accompanying consolidated statements of income. Amortization and impairment of other intangible assets, which consist primarily of customer relationships, trade names and covenants not to compete was $15.9 million and $17.2 million for the year ended December 31, 2018 and 2017 , respectively, and is classified as a component of Operating expenses in the accompanying consolidated statements of income. The Company monitors its intangible assets for indicators of impairment. If the Company determines that impairment has occurred, it writes-down the intangible asset to its fair value. For certain intangible assets where the unamortized balances exceed the undiscounted future net cash flow, the Company measures the amount of the impairment by calculating the amount by which the carrying values exceed the estimated fair values, which are based on projected discounted future net cash flows. During the year ended December 31, 2017 , the Company tested certain intangible assets for recoverability and, as a result, identified certain definite-lived intangible assets, primarily developed technology, that were impaired and recorded non-cash impairment charges of $18.0 million to write down the intangible assets to their estimated fair valu e of $1.6 million . Of the impairment charge, $15.5 million is included in Amortization and impairment of product related intangible assets and $2.5 million is included in Amortization and impairment of other intangible assets in the accompanying consolidated statements of income. These non-recurring fair value measurements were categorized as Level 3, as significant unobservable inputs were used in the valuation analysis. Key assumptions used in the valuation include forecasts of revenue and expenses over an extended period of time, customer retention rates, tax rates, and estimated costs of debt and equity capital to discount the projected cash flows. Certain of these assumptions involve significant judgment, are based on management’s estimate of current and forecasted market conditions and are sensitive and susceptible to change; therefore , further disruptions in the business could potentially result in additional amounts becoming impaired. Estimated future amortization expense of intangible assets with finite lives as of December 31, 2018 is as follows (in thousands): Year ending December 31, 2019 $ 50,981 2020 38,482 2021 24,494 2022 22,644 2023 19,292 Thereafter 11,294 Total $ 167,187 Software Development Costs The authoritative guidance requires certain internal software development costs related to software to be sold to be capitalized upon the establishment of technological feasibility. The Company's software development costs incurred subsequent to achieving technological feasibility have not been significant and substantially all software development costs have been expensed as incurred. Internal Use Software In accordance with the authoritative guidance, the Company capitalizes external direct costs of materials and services and internal costs such as payroll and benefits of those employees directly associated with the development of new functionality in internal use software. The amount of costs capitalized during the years ended 2018 and 2017 relating to internal use software was $14.8 million and $41.5 million , respectively. These costs are being amortized over the estimated useful life of the software, which is generally three to seven years, and are included in property and equipment in the accompanying consolidated balance sheets. The total amounts charged to expense relating to internal use software was approximately $25.9 million , $27.3 million and $37.8 million , during the years ended December 31, 2018 , 2017 and 2016 , respectively. The Company capitalized costs related to internally developed computer software to be sold as a service related to its Digital Workspace offerings, incurred during the application development stage, of $7.3 million and $15.2 million , during the years ended December 31, 2018 and 2017 , respectively, and is amortizing these costs over the expected lives of the related services, which is generally two years, and are included in property and equipment in the accompanying consolidated balance sheets. The total amounts charged to expense relating to internally developed computer software to be sold as a service was approximately $14.4 million , $18.5 million and $16.8 million , during the years ended December 31, 2018 , 2017 and 2016 , respectively, which are included in Cost of subscription, support and services. Pension Liability The Company provides retirement benefits to certain employees who are not U.S. based. Generally, benefits under these programs are based on an employee’s length of service and level of compensation. The majority of these programs are commonly referred to as termination indemnities, which provide retirement benefits in accordance with programs mandated by the governments of the countries in which such employees work. The Company had accrued $11.2 million and $13.2 million for these pension liabilities at December 31, 2018 and 2017 , respect

Discontinued Operations

Discontinued Operations	12 Months Ended
	Dec. 31, 2018
Discontinued Operations and Disposal Groups [Abstract]
DISCONTINUED OPERATIONS	DISCONTINUED OPERATIONS On January 31, 2017, the Company completed the Spin-off and its financial results are presented as (Loss) income from discontinued operations, net of income tax expense in the consolidated statements of income. The following table presents the financial results of the GoTo Business through the date of the Spin-off for the indicated periods and do not include corporate overhead allocations: 2017 2016 (in thousands) Net revenues $ 58,215 $ 682,185 Cost of net revenues 15,456 154,652 Gross margin 42,759 527,533 Operating expenses: Research and development 9,108 93,892 Sales, marketing and services 20,881 209,475 General and administrative 7,636 63,270 Amortization of other intangible assets 1,176 14,097 Restructuring 3,189 3,721 Separation 40,573 54,084 Total operating expenses 82,563 438,539 (Loss) income from discontinued operations before income taxes (39,804 ) 88,994 Income tax expense 2,900 22,737 (Loss) income from discontinued operations, net of income tax $ (42,704 ) $ 66,257 The Company incurred significant costs in connection with the separation of its GoTo Business, which were primarily included in discontinued operations. These costs relate primarily to third-party advisory and consulting services, retention payments to certain employees, incremental stock-based compensation and other costs directly related to the separation of the GoTo Business. During the years ended December 31, 2017 and 2016 , the Company incurred $0.5 million and $2.5 million of separation costs in continuing operations, which are included in General and administrative expense in the accompanying consolidated statements of income. As a result of the Spin-off, the Company recorded a $475.2 million reduction in retained earnings which included net assets of $461.8 million as of January 31, 2017. Of this amount, $28.5 million represents cash transferred to the GoTo Business, with the remainder considered a non-cash activity in the consolidated statements of cash flows. The Spin-off also resulted in a reduction of Accumulated other comprehensive loss associated with foreign currency translation adjustments of $13.4 million , which was reclassified to Retained earnings.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
ACQUISITIONS	ACQUISITIONS 2018 Business Combinations Sapho, Inc. On November 13, 2018, the Company acquired all of the issued and outstanding securities of Sapho, Inc. (“Sapho”), whose technology is intended to advance the Company’s development of the intelligent workspace. The acquired technology enables efficient workstyles by creating a unified and customizable notification experience for business applications. The total preliminary cash consideration for this transaction was $182.9 million , net of $3.7 million cash acquired. Transaction costs associated with the acquisition were not significant. Cedexis, Inc. On February 6, 2018, the Company acquired all of the issued and outstanding securities of Cedexis, Inc. (“Cedexis”) whose solution is a real-time data driven service for dynamically optimizing the flow of traffic across public clouds and data centers that provides a dynamic and reliable way to route and manage Internet performance for customers moving towards hybrid and multi-cloud deployments. The total cash consideration for this transaction was $66.0 million , net of $6.0 million cash acquired. Transaction costs associated with the acquisition were not significant. Purchase Accounting for the 2018 Business Combinations The purchase prices for the companies acquired during the year ended December 31, 2018 , which include Sapho and Cedexis (collectively, the "2018 Business Combinations"), were allocated to the respective acquired company's net tangible and intangible assets based on their estimated fair values as of the date of the acquisition. The allocation of the total purchase prices is summarized below (in thousands): Sapho Cedexis Purchase Price Allocation Asset Life Purchase Price Allocation Asset Life Current assets $ 4,671 $ 8,961 Intangible assets 53,600 5 years 27,200 1-6 years Goodwill 144,173 Indefinite 44,003 Indefinite Deferred taxes — 3,173 Other assets — 69 Assets acquired 202,444 83,406 Current liabilities assumed 3,323 5,711 Assumed debt — 5,674 Other long term liabilities assumed 370 — Deferred taxes 12,094 — Net assets acquired $ 186,657 $ 72,021 Current assets acquired in connection with the 2018 Business Combinations consisted primarily of cash, accounts receivable and other short-term assets. Current liabilities assumed in connection with the 2018 Business Combinations consisted primarily of accounts payable and other accrued expenses. Assumed debt for the Cedexis acquisition consisted primarily of short-term and long-term debt, which was paid in full subsequent to the acquisition date. The Company continues to evaluate certain assets and liabilities related to the Sapho acquisition that may be subject to change through the remainder of the measurement period, which will extend not more than twelve months from the acquisition date. The goodwill related to the 2018 Business Combinations is not deductible for tax purposes and is comprised primarily of expected synergies from combining operations and other intangible assets that do not qualify for separate recognition. Identifiable intangible assets acquired in connection with the 2018 Business Combinations (in thousands) and the weighted-average lives are as follows: Sapho Asset Life Cedexis Asset Life Customer relationships $ 1,600 5 years $ 2,000 1 year Developed technology 52,000 5 years 23,800 5-6 years Tradenames — 1,400 1 year Total $ 53,600 $ 27,200 The Company has included the effect of the 2018 Business Combinations in its results of operations prospectively from the date of acquisition. The following unaudited pro-forma information combines the consolidated results of the operations of the Company and the 2018 Business Combinations as if the acquisitions had occurred on January 1, 2017, the first day of the Company’s fiscal year 2017 (in thousands): Twelve Months Ended December 31 2018 2017 Revenues $ 2,977,155 $ 2,838,880 Income from continuing operations 651,047 530,470 Net income (loss) 550,985 (56,601 ) 2017 Business Combination On January 3, 2017, the Company acquired all of the issued and outstanding securities of Unidesk Corporation (“Unidesk”). The Company acquired Unidesk to enhance its application management and delivery offerings. The total cash consideration for this transaction was $60.4 million , net of $2.7 million of cash acquired. Transaction costs associated with the acquisition were not significant

Investments

Investments	12 Months Ended
	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
INVESTMENTS	INVESTMENTS Available-for-sale Investments Investments in available-for-sale securities at fair value were as follows for the periods ended (in thousands): December 31, 2018 December 31, 2017 Description of the Securities Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Agency securities $ 314,982 $ 333 $ (2,367 ) $ 312,948 $ 441,315 $ 509 $ (2,760 ) $ 439,064 Corporate securities 612,698 116 (4,156 ) 608,658 810,444 268 (3,020 ) 807,692 Municipal securities 2,500 4 — 2,504 3,965 2 (2 ) 3,965 Government securities 234,668 91 (935 ) 233,824 367,595 44 (1,516 ) 366,123 Total $ 1,164,848 $ 544 $ (7,458 ) $ 1,157,934 $ 1,623,319 $ 823 $ (7,298 ) $ 1,616,844 The change in net unrealized (losses) gains on available-for-sale securities recorded in Other comprehensive income (loss) includes unrealized (losses) gains that arose from changes in market value of specifically identified securities that were held during the period, gains (losses) that were previously unrealized, but have been recognized in current period net income due to sales and other than temporary impairments, as well as prepayments of available-for-sale investments purchased at a premium. See Note 16 for more information related to comprehensive income. The average remaining maturities of the Company’s short-term and long-term available-for-sale investments at December 31, 2018 were approximately 6 months and 2 years , respectively. Realized Gains and Losses on Available-for-sale Investments For the years ended December 31, 2018 and 2017 , the Company had realized gains on the sales of available-for-sale investments of $0.1 million and $0.8 million , respectively. For the years ended December 31, 2018 and 2017 , the Company had realized losses on available-for-sale investments of $1.5 million and $0.5 million , respectively, primarily related to sales of these investments during the period. All realized gains and losses related to the sales of available-for-sale investments are included in Other (expense) income, net , in the accompanying consolidated statements of income. Unrealized Losses on Available-for-Sale Investments The Company regularly reviews its investments for impairments based on criteria that include the duration of the market decline and the Company’s ability to hold its investment until recovery of its amortized cost basis. During the year ended December 31, 2018 , the Company recorded an other than temporary impairment of $4.6 million of certain available-for-sale securities, which was included in Other (expense) income, net in the accompanying consolidated statements of income. The gross unrealized losses on the Company’s available-for-sale investments that are not deemed to be other-than-temporarily impaired were $2.9 million and $7.3 million as of December 31, 2018 and 2017 , respectively. Because the Company does not intend to sell any of its investments in an unrealized loss position, other than as noted above, and it is more likely than not that it will not be required to sell the securities before the recovery of its amortized cost basis, which may not occur until maturity, it does not consider these securities to be other-than-temporarily impaired. Equity Securities without Readily Determinable Fair Values The Company held direct investments in privately-held companies of approximately $13.4 million as of December 31, 2018 , which are accounted for at cost, less impairment plus or minus adjustments resulting from observable price changes in orderly transactions for an identical or a similar investment of the same issuer. These investments are included in Other assets in the accompanying consolidated balance sheets. The Company periodically reviews these investments for impairment and observable price changes on a quarterly basis, and adjusts the carrying value accordingly. The Company determined that there were no material adjustments resulting from observable price changes to the Company’s investments in privately-held companies without a readily determinable fair value for the year ended December 31, 2018 . The fair value of these investments represents a Level 3 valuation as the assumptions used in valuing these investments are not directly or indirectly observable. See Note 6 for detailed information on fair value measurements. Equity Securities Accounted for at Net Asset Value The Company held equity interests in certain private equity funds of $10.9 million as of December 31, 2018 , which are accounted for under the net asset value practical expedient. These investments are included in Other assets in the accompanying consolidated balance sheets. The net asset value of these investments is determined using quarterly capital statements from the funds, which are based on the Company’s contributions to the funds, allocation of profit and loss and changes in fair value of the underlying fund investments. For 2017 , the Company’s investments in privately-held companies and private equity funds were previously classified as cost method investments and were $18.6 million as of December 31, 2017 . Due to the Company's adoption of the accounting standard update for the recognition and measurement of financial assets and liabilities, effective January 1, 2018, these investments are now accounted for under the new basis of accounting referenced above. See Note 2 for detailed information regarding the Company's recent accounting pronouncements.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS The authoritative guidance defines fair value as an exit price, representing the amount that would either be received to sell an asset or be paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the guidance establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: • Level 1. Observable inputs such as quoted prices in active markets for identical assets or liabilities; • Level 2 . Inputs, other than the quoted prices in active markets, that are observable either directly or indirectly; and • Level 3 . Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions. Available-for-sale securities included in Level 2 are valued utilizing inputs obtained from an independent pricing service (the “Service”) which uses quoted market prices for identical or comparable instruments rather than direct observations of quoted prices in active markets. The Service applies a four level hierarchical pricing methodology to all of the Company’s fixed income securities based on the circumstances. The hierarchy starts with the highest priority pricing source, then subsequently uses inputs obtained from other third-party sources and large custodial institutions. The Service’s providers utilize a variety of inputs to determine their quoted prices. These inputs may include interest rates, known historical trades, yield curve information, benchmark data, prepayment speeds, credit quality and broker/dealer quotes. Substantially all of the Company’s available-for-sale investments are valued utilizing inputs obtained from the Service and accordingly are categorized as Level 2 in the table below. The Company periodically independently assesses the pricing obtained from the Service and historically has not adjusted the Service's pricing as a result of this assessment. Available-for-sale securities are included in Level 3 when relevant observable inputs for a security are not available. The Company’s assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the classification of assets and liabilities within the fair value hierarchy. In certain instances, the inputs used to measure fair value may meet the definition of more than one level of the fair value hierarchy. The input with the lowest level priority is used to determine the applicable level in the fair value hierarchy. Assets and Liabilities Measured at Fair Value on a Recurring Basis As of December 31, 2018 Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (in thousands) Assets: Cash and cash equivalents: Cash $ 505,363 $ 505,363 $ — $ — Money market funds 88,126 88,126 — — Agency securities 3,296 — 3,296 — Corporate securities 9,371 — 9,371 — Government securities 12,610 12,610 — Available-for-sale securities: Agency securities 312,948 — 312,948 — Corporate securities 608,658 — 607,945 713 Municipal securities 2,504 — 2,504 — Government securities 233,824 — 233,824 — Prepaid expenses and other current assets: Foreign currency derivatives 764 — 764 — Total assets $ 1,777,464 $ 593,489 $ 1,183,262 $ 713 Accrued expenses and other current liabilities: Foreign currency derivatives 2,543 — 2,543 — Total liabilities $ 2,543 $ — $ 2,543 $ — As of December 31, 2017 Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (in thousands) Assets: Cash and cash equivalents: Cash $ 556,520 $ 556,520 $ — $ — Money market funds 555,826 555,826 — — Corporate securities 2,784 — 2,784 — Available-for-sale securities: Agency securities 439,064 — 439,064 — Corporate securities 807,692 — 807,299 393 Municipal securities 3,965 — 3,965 — Government securities 366,123 — 366,123 — Prepaid expenses and other current assets: Foreign currency derivatives 2,498 — 2,498 — Total assets $ 2,734,472 $ 1,112,346 $ 1,621,733 $ 393 Accrued expenses and other current liabilities: Foreign currency derivatives 814 — 814 — Total liabilities $ 814 $ — $ 814 $ — The Company’s fixed income available-for-sale security portfolio generally consists of investment grade securities from diverse issuers with a minimum credit rating of A-/A3 and a weighted-average credit rating of AA-/Aa3. The Company values these securities based on pricing from the Service, whose sources may use quoted prices in active markets for identical assets (Level 1 inputs) or inputs other than quoted prices that are observable either directly or indirectly (Level 2 inputs) in determining fair value, and accordingly, the Company classifies all of its fixed income available-for-sale securities as Level 2. The Company measures its cash flow hedges, which are classified as Prepaid expenses and other current assets and Accrued expenses and other current liabilities, at fair value based on indicative prices in active markets (Level 2 inputs). Assets Measured at Fair Value on a Non-recurring Basis Using Significant Unobservable Inputs (Level 3) During 2018 , certain direct investments in privately-held companies with a combined carrying value of $2.8 million were determined to be impaired and written down to their fair values of $1.9 million , resulting in impairment charges of $0.9 million . During 2017 , the Company determined that certain cost method investments with a combined carrying value of $2.6 million were determined to be impaired and have been written down to their fair values of $1.2 million resulting in impairment charges of $1.4 million . The impairment charges are included in Other (expense) income, net in the accompanying consolidated statements of income for the years ended December 31, 2018 and 2017 . In determining the fair value of the investments, the Company considers many factors including but not limited to operating performance of the investee, the amount of cash that the investee has on-hand, the ability to obtain additional financing and the overall market conditions in which the investee operates. Additional Disclosures Regarding Fair Value Measurements The carrying value of accounts receivable, accounts payable and accrued expenses approximate their fair value due to the short maturity of these items. As of December 31, 2018 , the fair value of the 2027 Notes and Convertible Notes, which was determined based on inputs that are observable in the market (Level 2), based on the closing trading price per $100 as of the last day of trading for the year ended December 31, 2018 , and carrying value of debt instruments (carrying value excludes the equity component of the Company’s Convertible Notes classified in equity) was as follows (in thousands): Fair Value Carrying Value 2027 Notes $ 717,375 $ 741,825 Convertible Senior Notes $ 1,648,567 $ 1,155,445 See Note 13 for more information on the 2027 Notes and Convertible Notes.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	12 Months Ended
	Dec. 31, 2018
Accounts Payable and Accrued Liabilities, Current [Abstract]
ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES	ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES Accrued expenses consist of the following: December 31, 2018 2017 (In thousands) Accrued compensation and employee benefits $ 196,847 $ 161,049 Other accrued expenses 93,645 116,630 Total $ 290,492 $ 277,679

Employee Stock-Based Compensati

Employee Stock-Based Compensation and Benefit Plans	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
EMPLOYEE STOCK-BASED COMPENSATION AND BENEFIT PLANS	EMPLOYEE STOCK-BASED COMPENSATION AND BENEFIT PLANS Plans The Company’s stock-based compensation program is a long-term retention program that is intended to attract and reward talented employees and align stockholder and employee interests. As of December 31, 2018 , the Company had one stock-based compensation plan under which it was granting equity awards. The Company is currently granting stock-based awards from its Amended and Restated 2014 Equity Incentive Plan (the "2014 Plan"), which was approved at the Company's Annual Meeting of Stockholders on June 22, 2017. In connection with certain of the Company’s acquisitions, the Company has assumed certain plans from acquired companies. The Company’s Board of Directors has provided that no new awards will be granted under the Company’s acquired stock plans. Awards previously granted under the Company's superseded stock plans that are still outstanding typically expire between five and ten years from the date of grant and will continue to be subject to all the terms and conditions of such plans, as applicable. The Company’s superseded stock plans with outstanding awards include the Amended and Restated 2005 Equity Incentive Plan ("2005 Plan"). Under the terms of the 2014 Plan, the Company is authorized to grant incentive stock options (“ISOs”), non-qualified stock options (“NSOs”), non-vested stock, non-vested stock units, stock appreciation rights (“SARs”), and performance units and to make stock-based awards to full and part-time employees of the Company and its subsidiaries or affiliates, where legally eligible to participate, as well as to consultants and non-employee directors of the Company. ISOs, NSOs and SARs are not currently being granted. Currently, the 2014 Plan provides for the issuance of 46,000,000 shares of common stock. In addition, shares of common stock underlying any awards granted under the Company’s 2014 Plan or the 2005 Plan that are forfeited, canceled or otherwise terminated (other than by exercise) are added to the shares of common stock available for issuance under the 2014 Plan. Under the 2014 Plan, NSOs must be granted at exercise prices no less than fair market value on the date of grant. Non-vested stock awards may be granted for such consideration in cash, other property or services, or a combination thereof, as determined by the Company’s Compensation Committee of its Board of Directors. Stock-based awards are generally exercisable or issuable upon vesting. The Company’s policy is to recognize compensation cost for awards with only service conditions and a graded vesting schedule on a straight-line basis over the requisite service period for the entire award. As of December 31, 2018 , there were 20,837,415 shares of common stock reserved for issuance pursuant to the Company’s stock-based compensation plans, including authorization under its 2014 Plan to grant stock-based awards covering 14,935,686 shares of common stock. In December 2014, the Company’s Board of Directors approved the 2015 Employee Stock Purchase Plan (the “2015 ESPP”), which was approved by stockholders at the Company’s Annual Meeting of Stockholders held on May 28, 2015. Under the 2015 ESPP, all full-time and certain part-time employees of the Company are eligible to purchase common stock of the Company twice per year at the end of a six -month payment period (a “Payment Period”). During each Payment Period, eligible employees who so elect may authorize payroll deductions in an amount no less than 1% nor greater than 10% of his or her base pay for each payroll period in the Payment Period. At the end of each Payment Period, the accumulated deductions are used to purchase shares of common stock from the Company up to a maximum of 12,000 shares for any one employee during a Payment Period. Shares are purchased at a price equal to 85% of the fair market value of the Company’s common stock, on either the first business day of the Payment Period or the last business day of the Payment Period, whichever is lower. Employees who, after exercising their rights to purchase shares of common stock in the 2015 ESPP, would own shares representing 5% or more of the voting power of the Company’s common stock, are ineligible to continue to participate under the 2015 ESPP. The 2015 ESPP provides for the issuance of a maximum of 16,000,000 shares of common stock. As of December 31, 2018 , 1,721,924 shares have been issued under the 2015 ESPP. The Company recorded stock-based compensation costs related to its employee stock purchase plan of $9.8 million , $10.0 million and $7.5 million for the years ended December 31, 2018 , 2017 and 2016 , respectively. The Company used the Black-Scholes model to estimate the fair value of the 2015 ESPP awards with the following weighted-average assumptions: Year Ended Year Ended Year Ended December 31, 2018 December 31, 2017 December 31, 2016 Expected volatility factor 0.26 - 0.29 0.27 - 0.29 0.27 - 0.41 Risk free interest rate 1.12% - 2.19% 0.60% - 1.12% 0.25% - 0.42% Expected dividend yield 0% - 1.27% 0 % 0 % Expected life (in years) 0.5 0.5 0.5 The Company determined the expected volatility factor by considering the implied volatility in six-month market-traded options of the Company's common stock based on third party volatility quotes. The Company's decision to use implied volatility was based upon the availability of actively traded options on the Company's common stock and its assessment that implied volatility is more representative of future stock price trends than historical volatility. The risk-free interest rate was based on a U.S. Treasury instrument whose term is consistent with the expected term of the stock options. The Company's historical dividend yield input was zero in prior periods as it has not historically paid cash dividends on its common stock. The current dividend yield has been updated for expected dividend yield payout given the Company started paying a recurring quarterly dividend beginning in December 2018. The expected term is based on the term of the purchase period for grants made under the ESPP. Expense Information As required by the authoritative guidance prior to January 1, 2017, the Company estimated forfeitures of stock awards and recognized compensation costs only for those awards expected to vest. Forfeiture rates were determined based on historical experience. The Company also considered whether there had been any significant changes in facts and circumstances that would affect its forfeiture rate quarterly. Estimated forfeitures were adjusted to actual forfeiture experience as needed. Subsequent to January 1, 2017, in connection with the adoption of an accounting standard update, the Company made a policy election to account for forfeitures as they occur rather than on an estimated basis. The Company recorded stock-based compensation costs, related deferred tax assets and tax benefits of $203.6 million , $39.7 million and $49.7 million , respectively, in 2018 , $165.1 million , $46.1 million and $72.9 million , respectively, in 2017 and $152.7 million , $53.5 million and $64.7 million , respectively, in 2016 . The detail of the total stock-based compensation recognized by income statement classification is as follows (in thousands): Income Statement Classifications 2018 2017 2016 Cost of subscription, support and services $ 7,979 $ 4,281 $ 2,179 Research and development 66,154 47,291 38,578 Sales, marketing and services 72,406 55,173 48,514 General and administrative 57,080 58,375 63,468 Total $ 203,619 $ 165,120 $ 152,739 Non-vested Stock Units Market Performance and Service Condition Stock Units In March 2017, the Company granted senior level employees non-vested stock unit awards representing, in the aggregate, 275,148 non-vested stock units that vest based on certain target performance and service conditions. The number of non-vested stock units underlying the award will be determined within sixty days of the three -year performance period ending December 31, 2019. The attainment level under the award will be based on the Company's relative total return to stockholders over the performance period compared to a pre-established custom index group. If the Company’s relative total return to stockholders is between the 41st percentile and the 80th percentile when compared to the index companies, the number of non-vested stock units earned will be based on interpolation. The maximum number of non-vested stock units that may vest pursuant to the awards is capped at 200% of the target number of non-vested stock units set forth in the award agreement and is earned if the Company's relative total return to stockholders when compared to the index companies is at or greater than the 80th percentile. If the Company’s total return to stockholders is negative, the number of non-vested stock units earned will be no more than 100% regardless of the Company’s relative total return to stockholders compared to the index companies. If the awardee is not employed by the Company at the end of the performance period, the extent to which the awardee will vest in the award, if at all, is dependent upon the timing and character of the termination as provided in the award agreement. Each non-vested stock unit, upon vesting, represents the right to receive one share of the Company's common stock. Certain awards for senior level employees, none of whom were executive officers, were modified in December 2018 to replace the pre-established custom index group used to measure performance and related award payout to companies that are part of the Nasdaq Composite index. As a result, the awards were revalued as of the modification date. The impact of the modification was not material to the consolidated financial statements. In January 2016, the Company granted its former Chief Executive Officer 220,235 non-vested stock units that vest based on certain target performance conditions; and in March 2016, the Company granted senior level employees 234,816 non-vested stock units that vest based on certain target performance conditions. These awards were modified as a result of the Spin-off whereby the opening stock price related to the awards was updated to reflect the value of the shares of LogMeIn stock distributed to the Company's shareholders. The attainment level under the awards will be based on the Company's compound annualized total return to stockholders over a three -year performance period, with 100% of such stock units earned if the Company achieves total shareholder return of 10% over the performance period. Further, if the Company achieves annualized total shareholder return of less than 10% during the performance period, the awardees may earn all or a portion of the target award, but not in excess of 100% of such stock units, depending upon the Company’s relative total shareholder return compared to companies listed in the S&P Computer Software Select Index. If the Company's compound annualized total shareholder return is 5% or above, the number of non-vested stock units earned will be based on interpolation, with the maximum number of non-vested stock units earned capped at 200% of the target number of non-vested stock units for a compound annualized total return to stockholders of 30% over a three-year performance period as set forth in the award agreement. Within sixty days following an interim measurement period of 18 months, the Compensation Committee will determine the number of restricted stock units that would be deemed earned based on performance to date, and up to 33% of the target award may be earned based on such performance; however, any stock units that are deemed earned will remain subject to continued service vesting until the end of the three-year performance period, or a change in control, if earlier. Within sixty days following the conclusion of the performance period, the Company’s Compensation Committee will determine the number of restricted stock units that would vest upon the final day of the performance period based on the Company’s performance during the period and in accordance with the terms of the award. On the vesting date, the greater of the full period restricted stock units, or the interim earned restricted stock units, will vest in one installment. The market condition requirements are reflected in the grant date fair value of the award, and the compensation expense for the award will be recognized assuming that the requisite service is rendered regardless of whether the market conditions are achieved. The grant date fair value of the non-vested performance stock unit awards was determined through the use of a Monte Carlo simulation model, which utilized multiple input variables that determined the probability of satisfying the market condition requirements applicable to each award as follows: March 2017 Grant (Modified) March 2017 Grant March 2016 Grant January 2016 Grant Expected volatility factor 0.16 - 0.32 0.27 - 0.32 0.29 - 0.39 0.29 - 0.37 Risk free interest rate 2.67 % 1.48 % 0.91 % 1.10 % Expected dividend yield 0 % 0 % 0 % 0 % For the unmodified March 2017 grant, the range of expected volatilities utilized was based on the historical volatilities of the Company's common stock and the average of its peer group. The Company chose to use historical volatility to value these awards because historical stock prices were used to develop the correlation coefficients between the Company and its peer group in order to model the stock price movements. The volatilities used were calculated over the most recent 2.75 year period, which is commensurate with the awards' performance period at the date of grant. The risk free interest rate was based on the implied yield available on U.S. Treasury zero-coupon issues with remaining terms equivalent to the performance period. The Company used a zero dividend yield input for this award as it had not historically paid cash dividends on its common stock as of the grant date of this award. The estimated fair value of each award as of the date of grant was $104.05 . For the modified March 2017 grant, all input variables chosen are as of the modification date. The range of expected volatilities utilized was based on the historical volatilities of the Company's common stock and the average of the Nasdaq Composite index peer group. The Company chose to use historical volatility to value these awards because historical stock prices were used to develop the correlation coefficients between the Company and its peer group in order to model the stock price movements. The volatilities used were calculated over the most recent 1.06 year period, which is commensurate with the awards' remaining performance period at the modification date. The risk free interest rate was based on the implied yield available on U.S. Treasury zero-coupon issues with remaining terms equivalent to the remaining performance period. The Company used a zero dividend yield input for this award as dividends are assumed to be reinvested. The estimated incremental fair value of each modified award as of the modification date was $99.54 . For the March 2016 and January 2016 grants, the range of expected volatilities utilized was based on the historical volatilities of the Company's common stock and the average of its peer group. The Company chose to use historical volatility to value these awards because historical stock prices were used to develop the correlation coefficients between the Company and its peer group in order to model the stock price movements. The volatilities used were calculated over a 3.00 year period, which is commensurate with the awards’ performance period at the date of grant. The risk free interest rate was based on the implied yield available on U.S. Treasury zero-coupon issues with remaining terms equivalent to the performance period. The Company used a zero dividend yield input for this award as it had not historically paid cash dividends on its common stock as of the grant date of this award. The estimated fair value of each award as of the date of grant was $66.18 for the March 2016 grant and $49.68 for the January 2016 grant. Service Based Stock Units The Company also awards senior level employees, certain other employees and new non-employee directors, non-vested stock units granted under the 2014 Plan that vest based on service. The majority of these non-vested stock unit awards generally vest 33.33% on each anniversary subsequent to the date of the award. The Company also assumes non-vested stock units in connection with certain of its acquisitions. The assumed awards have the same three year vesting schedule. Each non-vested stock unit, upon vesting, represents the right to receive one share of the Company’s common stock. In addition, the Company awards non-vested stock units to all of its continuing non-employee directors. These awards vest monthly in 12 equal installments based on service and, upon vesting, each stock unit represents the right to receive one share of the Company's common stock. Company Performance Stock Units In March 2018, the Company awarded senior level employees 268,729 non-vested performance stock unit awards granted under the 2014 Plan. The number of non-vested stock units underlying the award will be determined within sixty days following completion of the performance period ending December 31, 2020 and will be based on the achievement of specific corporate financial performance goals related to subscription bookings as a percentage of total product bookings measured during the period from January 1, 2020 to December 31, 2020. As defined in the applicable award agreements, total product bookings includes subscription bookings. The number of non-vested stock units issued will be based on a graduated slope, with the maximum number of non-vested stock units issuable pursuant to the award capped at 200% of the target number of non-vested stock units set forth in the award agreement. The Company is required to estimate the attainment expected to be achieved related to the defined performance goals and the number of non-vested stock units that will ultimately be awarded in order to recognize compensation expense over the vesting period. Each non-vested stock unit, upon vesting, represents the right to receive one share of the Company’s common stock. Compensation expense will be recorded through the end of the performance period on December 31, 2020 if it is deemed probable that the performance goals will be met. If the performance goals are not met, no compensation cost will be recognized and any previously recognized compensation cost will be reversed. On August 1, 2017, the Company awarded certain senior level employees 184,322 non-vested performance stock unit awards granted under the 2014 Plan. The number of non-vested stock units underlying each award will be determined within sixty days of the calendar year following completion of the performance period ending December 31, 2019 and will be based on achievement of specific corporate financial performance goals related to non-GAAP net operating margin and subscription bookings as a percent of total product bookings measured during the period from January 1, 2019 to December 31, 2019. As defined in the applicable award agreements, total product bookings includes subscription bookings. The number of non-vested stock units issued will be based on a graduated slope, with the maximum number of non-vested stock units issuable pursuant to the award capped at 200% of the target number of non-vested stock units set forth in the award agreement. The Company is required to estimate the attainment expected to be achieved related to the defined performance goals and the number of non-vested stock units that will ultimately be awarded in order to recognize compensation expense over the vesting period. Each non-vested stock unit, upon vesting, represents the right to receive one share of the Company’s common stock. The non-GAAP net operating margin and subscription bookings as a percent of total product targets were set in the first quarter of 2018. As a result, such awards were not outstanding for U.S. GAAP until the first quarter of 2018 when the performance goals were determined and subsequently communicated to employees who received these awards. Compensation expense will be recorded through the end of the performance period on December 31, 2019 if it is deemed probable that the performance goals will be met. If the performance goals are not met, no compensation cost will be recognized and any previously recognized compensation cost will be reversed. Non Vested Stock Unit Activity for the Year The following table summarizes the Company's non-vested stock unit activity for the year ended December 31, 2018 : Number of Shares Weighted- Average Fair Value at Grant Date Non-vested stock units at December 31, 2017 4,622,546 $ 82.83 Granted 3,903,225 92.20 Vested (2,076,052 ) 71.92 Forfeited (596,218 ) 74.07 Non-vested stock units at December 31, 2018 5,853,501 88.79 For the years ended December 31, 2018 , 2017 and 2016 , the Company recognized stock-based compensation expense of $193.8 million , $149.8 million and $135.7 million , respectively, related to non-vested stock units. The fair value of the non-vested stock units released in 2018 , 2017 , and 2016 was $149.3 million , $150.0 million and $163.8 million , respectively. As of December 31, 2018 , there was $376.7 million of total unrecognized compensation cost related to non-vested stock units. The unrecognized cost is expected to be recognized over a weighted-average period of 1.76 years. Benefit Plan The Company maintains a 401(k) benefit plan allowing eligible U.S.-based employees to contribute up to 90% of their annual eligible earnings to the plan on a pretax and after-tax basis, including Roth contributions, limited to an annual maximum amount as set periodically by the IRS. The Company, at its discretion, may contribute up to $ 0.50 for each dollar of employee contribution. The Company’s total matching contribution to an employee is typically made at 3% of the employee’s annual compensation. The Company’s matching contributions were $13.0 million , $13.7 million and $14.0 million in 2018 , 2017 and 2016 , respectively. The Company’s matching contributions vest immediately.

Capital Stock

Capital Stock	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
CAPITAL STOCK	CAPITAL STOCK Stock Repurchase Programs The Company’s Board of Directors authorized an ongoing stock repurchase program, of which $1.7 billion was approved in November 2017 and $750.0 million was approved in October 2018. The Company may use the approved dollar authority to repurchase stock at any time until the approved amount is exhausted. The objective of the Company’s stock repurchase program is to improve stockholders’ returns. At December 31, 2018 , approximately $767.9 million was available to repurchase common stock pursuant to the stock repurchase program. All shares repurchased are recorded as treasury stock. A portion of the funds used to repurchase stock over the course of the program was provided by net proceeds from the Convertible Notes and 2027 Notes offerings, as well as proceeds from employee stock awards exercises and the related tax benefit. The Company is authorized to make open market purchases of its common stock using general corporate funds through open market purchases, pursuant to a Rule 10b5-1 plan or in privately negotiated transactions. In November 2017, the Company purchased $750.0 million of shares of its common stock through the ASR agreement with the ASR counterparty. The Company paid $750.0 million to the ASR counterparty under the ASR agreement and received approximately 7.1 million shares of its common stock from the ASR counterparty, which represented 80 percent of the value of the shares to be repurchased pursuant to the ASR agreement. The total number of shares of common stock that the Company repurchased under the ASR agreement was based on the average of the daily volume-weighted average prices of its common stock during the term of the ASR agreement, less a discount. Final settlement of the ASR agreement was completed in January 2018 and the Company received delivery of an additional 1.4 million shares of its common stock. In February 2018, the Company entered into an ASR transaction with a counterparty to pay an aggregate of $750.0 million in exchange for the immediate delivery of approximately 6.5 million shares of its common stock based on current market prices. The purchase price per share under the ASR was based on the volume-weighted average price of the Company's common stock during the term of the ASR, less a discount. The ASR was entered into pursuant to the Company's existing share repurchase program. Final settlement of the ASR agreement was completed in April 2018 and the Company received delivery of an additional 1.6 million additional shares of its common stock. During the year ended December 31, 2018 , the Company expended approximately $511.2 million on open market purchases under the stock repurchase program, repurchasing 4,730,542 shares of outstanding common stock at an average price of $108.05 During the year ended December 31, 2017 , the Company expended approximately $575.0 million on open market purchases under the stock repurchase program, repurchasing 7,384,368 shares of outstanding common stock at an average price of $77.86 . During the year ended December 31, 2016 , the Company expended approximately $28.7 million on open market purchases under the stock repurchase program, repurchasing 426,300 shares of outstanding common stock at an average price of $67.30 . Shares for Tax Withholding During the years ended December 31, 2018 , 2017 and 2016 , the Company withheld 739,522 shares, 974,501 shares and 830,155 shares, respectively, from equity awards that vested. Amounts withheld to satisfy minimum tax withholding obligations that arose on the vesting of equity awards was $71.6 million , $80.0 million and $66.6 million , for 2018 , 2017 and 2016 , respectively. These shares are reflected as treasury stock in the Company's consolidated balance sheets and the related cash outlays do not reduce the Company's total stock repurchase authority. Preferred Stock The Company is authorized to issue 5,000,000 shares of preferred stock, $0.01 par value per share. No shares of such preferred stock were issued and outstanding at December 31, 2018 or 2017 . Cash Dividend On October 24, 2018, the Company announced that its Board of Directors approved a quarterly cash dividend of $0.35 per share which was paid on December 21, 2018 to all shareholders of record as of the close of business on December 7, 2018. Subsequent Event On January 23, 2019, the Company announced that its Board of Directors approved a quarterly cash dividend of $0.35 per share. This dividend is payable on March 22, 2019 to all shareholders of record as of the close of business on March 8, 2019. Future dividends will be subject to Board approval.

Commitments And Contingencies

Commitments And Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Leases The Company leases certain office space and equipment under various operating leases. In addition to rent, the leases require the Company to pay for taxes, insurance, maintenance and other operating expenses. Certain of these leases contain stated escalation clauses while others contain renewal options. The Company recognizes rent expense on a straight-line basis over the term of the lease, excluding renewal periods, unless renewal of the lease is reasonably assured. Rental expense for the year ended December 31, 2018 totaled approximately $73.8 million , of which $14.2 million related to charges for the consolidation of leased facilities related to restructuring activities. Rental expense for the year ended December 31, 2017 totaled approximately $64.3 million , of which $9.7 million related to charges for the consolidation of leased facilities related to restructuring activities. Rental expense for the year ended December 31, 2016 totaled approximately $84.6 million , of which $28.9 million related to charges for the consolidation of leased facilities related to restructuring activities. Sublease income for the years ended December 31, 2018 , 2017 and 2016 was approximately $0.2 million , $0.2 million and $0.2 million , respectively. Lease commitments under non-cancelable operating leases with initial or remaining terms in excess of one year and sublease income associated with non-cancelable subleases, are as follows: Operating Leases Sublease Income (In thousands) Years ending December 31, 2019 $ 57,122 $ 241 2020 49,358 — 2021 39,981 — 2022 35,296 — 2023 32,018 — Thereafter 87,621 — Total $ 301,396 $ 241 Liabilities for Loss on Lease Obligations The Company recognizes liabilities for costs that will continue to be incurred under operating lease obligations for their remaining terms without economic benefit to the Company. The liabilities are measured and recorded at their fair values as of the cease-use date (the date the Company vacates the leased space and no longer derives economic benefit from the leases). The liabilities are included in Accrued expenses and other current liabilities and Other long-term liabilities in the consolidated balance sheets and the related expense is included in Restructuring expenses in the consolidated statements of income. The fair values of the liabilities are determined by discounting certain future cash flows related to the leases using a credit-adjusted risk-free interest rate as of the cease-use date (Level 3). The future cash flows that are discounted include the remaining base rentals due under the leases, reduced by the estimated sublease rentals that could be reasonably obtained for the properties even if the Company has no intention to enter into a sublease. The estimate of sublease rentals may change, which would require future changes to the liabilities for loss on lease obligations. As of December 31, 2018 , the Company's liabilities for loss on lease obligations total approximately $43.4 million , of which approximately $42.3 million relates to one office location. The calculation of these liabilities requires judgment in estimating the timing of securing subleases for the vacant space, as well as the terms of possible subleases, including the length of the sublease periods, sublease rentals, rent concessions and other tenant incentives. While the Company believes that the assumptions used in the calculation of these liabilities are reasonable, due to the inherent uncertainties related to such assumptions, there can be no assurance that the Company will be able to secure such subleases within the timing assumed in its calculations, or at all, and with terms consistent with the assumptions used. In this office location, if the price per square foot assumption were to change by $0.50 or approximately 20% , it would impact the estimate of sublease rentals, which would result in a change of $4.9 million to the liabilities for loss on lease obligation. Legal Matters The Company accrues a liability for legal contingencies when it believes that it is both probable that a liability has been incurred and that it can reasonably estimate the amount of the loss. The Company reviews these accruals and adjusts them to reflect ongoing negotiations, settlements, rulings, advice of legal counsel and other relevant information. To the extent new information is obtained and the Company's views on the probable outcomes of claims, suits, assessments, investigations or legal proceedings change, changes in the Company's accrued liabilities would be recorded in the period in which such determination is made. In addition, in accordance with the relevant authoritative guidance, for matters in which the likelihood of material loss is at least reasonably possible, the Company provides disclosure of the possible loss or range of loss. If a reasonable estimate cannot be made, however, the Company will provide disclosure to that effect. Due to the nature of the Company's business, the Company is subject to patent infringement claims, including current suits against it or one or more of its wholly-owned subsidiaries alleging infringement by various Company solutions and services. The Company believes that it has meritorious defenses to the allegations made in its pending cases and intends to vigorously defend these lawsuits; however, it is unable currently to determine the ultimate outcome of these or similar matters or the potential exposure to loss, if any. In addition, the Company is a defendant in various litigation matters generally arising out of the normal course of business. Although it is difficult to predict the ultimate outcomes of these cases, the Company believes that it is not reasonably possible that the ultimate outcomes will materially and adversely affect its business, financial position, results of operations or cash flows. Guarantees The authoritative guidance requires certain guarantees to be recorded at fair value and requires a guarantor to make disclosures, even when the likelihood of making any payments under the guarantee is remote. For those guarantees and indemnifications that do not fall within the initial recognition and measurement requirements of the authoritative guidance, the Company must continue to monitor the conditions that are subject to the guarantees and indemnifications, as required under existing generally accepted accounting principles, to identify if a loss has been incurred. If the Company determines that it is probable that a loss has been incurred, any such estimable loss would be recognized. The initial recognition and measurement requirements do not apply to the provisions contained in the majority of the Company’s software license agreements that indemnify licensees of the Company’s software from damages and costs resulting from claims alleging that the Company’s software infringes the intellectual property rights of a third party. The Company has not made material payments pursuant to these provisions as of December 31, 2018 . The Company has not identified any losses that are probable under these provisions and, accordingly, the Company has not recorded a liability related to these indemnification provisions. Purchase Obligations The Company has agreements with suppliers to purchase inventory and estimates its non-cancelable obligations under these agreements for the fiscal year ended December 31, 2019 to be approximately $5.3 million . The Company also has contingent obligations to purchase inventory for the fiscal year ended December 31, 2019 of approximately $16.6 million . The Company does not have any purchase obligations beyond December 31, 2019 . Other Purchase Commitments In June 2018, the Company entered into an amended agreement with a third-party provider for the Company's use of certain cloud services through June 2021. Under the amended agreement, the Company is committed to a purchase of $25.0 million in fiscal year 2019 and $25.0 million in fiscal year 2020.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company is required to estimate its income taxes in each of the jurisdictions in which it operates as part of the process of preparing its consolidated financial statements. The Company maintains certain strategic management and operational activities in overseas subsidiaries and its foreign earnings are taxed at rates that are generally lower than in the United States. On December 22, 2017, President Donald Trump signed the Tax Cuts and Jobs Act (the “2017 Tax Act”) into law effective January 1, 2018. The 2017 Tax Act significantly revised the U.S. tax code by, in part but not limited to: reducing the U.S. corporate maximum tax rate from 35% to 21%, imposing a mandatory one-time transition tax on certain un-repatriated earnings of foreign subsidiaries, modifying executive compensation deduction limitations, and repealing the deduction for domestic production activities. Under Accounting Standards Codification 740, Income Taxes, the Company must recognize the effects of tax law changes in the period in which the new legislation is enacted. The SEC staff acknowledged the challenges companies face incorporating the effects of the 2017 Tax Act by their financial reporting deadlines. In response, on December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”) to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed in reasonable detail to complete accounting for certain income tax effects of the 2017 Tax Act. During the period ended December 31, 2018, the Company completed the accounting for the tax effects of all of the provisions of the 2017 Tax Act within the required measurement period and as a result recorded adjustments to the previous provisional amounts. Adjustments recorded during the period ended December 31, 2018 include in part a tax benefit of $26.3 million attributable to a tax benefit of $21.9 million related to the finalization of the one-time transition tax on deemed repatriation of foreign income and a tax benefit of $4.4 million related to the finalization of the remeasurement of the U.S. deferred tax assets and liabilities due to the maximum U.S. federal corporate rate reduction from 35% to 21%. The United States and foreign components of income before income taxes are as follows: 2018 2017 2016 (In thousands) United States $ 174,519 $ 78,897 $ 59,344 Foreign 454,936 471,449 468,426 Total $ 629,455 $ 550,346 $ 527,770 The components of the provision for income taxes are as follows: 2018 2017 2016 (In thousands) Current: Federal $ (19,461 ) $ 374,602 $ 18,832 Foreign 70,146 56,526 52,978 State 16,259 3,075 7,759 Total current 66,944 434,203 79,569 Deferred: Federal 1,899 52,842 (7,688 ) Foreign (14,804 ) (5,468 ) (3,139 ) State (251 ) 46,784 (10,827 ) Total deferred (13,156 ) 94,158 (21,654 ) Total provision $ 53,788 $ 528,361 $ 57,915 The following table presents the breakdown of net deferred tax assets: December 31, 2018 2017 (In thousands) Deferred tax assets $ 136,998 $ 152,362 Deferred tax liabilities (15,075 ) (237 ) Total net deferred tax assets $ 121,923 $ 152,125 The significant components of the Company’s deferred tax assets and liabilities consisted of the following: December 31, 2018 2017 (In thousands) Deferred tax assets: Accruals and reserves $ 27,022 $ 30,317 Deferred revenue 62,085 65,016 Tax credits 81,720 80,772 Net operating losses 54,747 36,674 Stock based compensation 30,936 21,714 Depreciation and amortization — 4,939 Valuation allowance (85,400 ) (76,789 ) Total deferred tax assets 171,110 162,643 Deferred tax liabilities: Acquired technology (15,681 ) (2,882 ) Depreciation and amortization (5,044 ) — Prepaid expenses (23,213 ) (7,414 ) Other (5,249 ) (222 ) Total deferred tax liabilities (49,187 ) (10,518 ) Total net deferred tax assets $ 121,923 $ 152,125 The authoritative guidance requires a valuation allowance to reduce the deferred tax assets reported if it is not more likely than not that some portion or all of the deferred tax assets will be realized. At December 31, 2018 , the Company determined an $85.4 million valuation allowance was necessary, which relates to deferred tax assets for net operating losses and tax credits that may not be realized. At December 31, 2018 , the Company retained $172.3 million of remaining net operating loss carry forwards in the United States from acquisitions. The utilization of these net operating loss carry forwards are limited in any one year pursuant to Internal Revenue Code Section 382 and may begin to expire in 2019. At December 31, 2018 , the Company held $111.3 million of remaining net operating loss carry forwards in foreign jurisdictions that begin to expire in 2022. At December 31, 2018 , the Company held $116.6 million of federal and state research and development tax credit carry forwards in the United States, a portion of which may begin to expire in 2019. A reconciliation of the Company’s effective tax rate to the statutory federal rate is as follows: Year Ended December 31, 2018 2017 2016 Federal statutory taxes 21.0 % 35.0 % 35.0 % State income taxes, net of federal tax benefit 0.7 2.1 0.8 Foreign operations (5.4 ) (20.0 ) (21.6 ) Permanent differences 2.0 2.6 3.2 The 2017 Tax Act - tax rate impact on deferred taxes (0.7 ) 11.8 — The 2017 Tax Act - transition tax (3.5 ) 66.3 — Change in valuation allowance reserve 0.4 8.8 — Change in deferred tax liability related to acquired intangibles (0.1 ) 0.3 (0.8 ) Tax credits (5.8 ) (7.6 ) (7.9 ) Stock-based compensation (1.9 ) (3.6 ) 0.3 Change in accruals for uncertain tax positions 1.8 0.3 2.2 Other — — (0.2 ) 8.5 % 96.0 % 11.0 % The Company’s effective tax rate generally differs from the U.S. federal statutory rate primarily due to lower tax rates on earnings generated by the Company’s foreign operations that are taxed primarily in Switzerland. The 2017 Tax Act subjects a U.S. shareholder to tax on global intangible low-taxed income (“GILTI”) earned by certain foreign subsidiaries. The FASB Staff Q&A, Topic 740, No. 5, Accounting for Global Intangible Low-Taxed Income provides that an entity may make an accounting policy election to either recognize deferred taxes for temporary basis differences expected to reverse as GILTI in future years, or provide for the tax expense related to GILTI in the year the tax is incurred as a period expense only. Additionally, the 2017 Tax Act provides for a tax benefit to U.S. taxpayers that sell goods or services to foreign customers under the new Foreign Derived Intangible Income Deduction ("FDII") rules. As of December 31, 2018 , the Company concluded to provide for the GILTI tax expense and FDII benefit in the year the tax is incurred and as a result the Company included federal and state GILTI and FDII amounts of $12.8 million expense and $5.4 million benefit, respectively, related to current-year operations only in its estimated annual effective tax rate and has not provided additional GILTI on deferred items. The Company's effective tax rate was approximately 8.5% and 96.0% for the years ended December 31, 2018 and 2017 , respectively. The decrease in the effective tax rate when comparing the year ended December 31, 2018 to the year ended December 31, 2017 was primarily due to accounting for the estimated tax impact of the 2017 Tax Act and the separation of the GoTo Business. Specifically, results from 2017 include a $364.6 million provisional income tax charge for the transition tax on deemed repatriation of deferred foreign income, and a $64.8 million provisional income tax charge for the remeasurement of U.S. deferred tax assets and liabilities because of the maximum U.S. federal corporate rate reduction from 35% to 21% . The Company also recorded a $48.6 million income tax charge to establish a valuation allowance primarily due to a change in expectation of realizability of state R&D credits arising from the separation of the GoTo Business. During the year ended December 31, 2018 , the Company recorded a tax benefit of $21.9 million related to the finalization of the one-time transition tax on deemed repatriation of foreign income and a tax benefit of $4.4 million related to the finalization of the remeasurement of U.S. deferred tax assets and liabilities because of the maximum U.S. federal corporate rate reduction from 35% to 21% . The Company's effective tax rate was approximately 96.0% and 11.0% for the years ended December 31, 2017 and 2016 , respectively. The increase in the effective tax rate when comparing the year ended December 31, 2017 to the year ended December 31, 2016 was primarily due to accounting for the estimated tax impact of the 2017 Tax Act and the separation of the GoTo Business. Specifically, the Company recorded a $364.6 million provisional income tax charge for the transition tax on deemed repatriation of deferred foreign income, and a $64.8 million provisional income tax charge for the remeasurement of U.S. deferred tax assets and liabilities because of the maximum U.S. federal corporate rate reduction from 35% to 21% . The Company also recorded a $48.6 million income tax charge to establish a valuation allowance primarily due to a change in expectation of realizability of state R&D credits arising from the separation of the GoTo Business. These charges were marginally offset by a $22.0 million tax benefit due to the adoption of an accounting standard update requiring recognition of income tax effects related to stock based compensation when the awards vest or settle. A reconciliation of the beginning and ending amount of unrecognized tax benefits for the years ended December 31, 2018 and 2017 is as follows (in thousands): Balance at December 31, 2016 $ 69,801 Additions based on tax positions related to the current year 9,293 Additions for tax positions of prior years 7,656 Reductions related to audit settlements (137 ) Reductions related to the expiration of statutes of limitations (8,764 ) Balance at December 31, 2017 77,849 Additions based on tax positions related to the current year 10,168 Additions for tax positions of prior years 10,325 Reductions related to the expiration of statutes of limitations (8,436 ) Balance at December 31, 2018 $ 89,906 As of December 31, 2018 , unrecognized tax benefits of $35.4 million were offset against long-term deferred tax assets. All amounts included in this balance affect the annual effective tax rate. The Company recognizes interest accrued related to uncertain tax positions and penalties in income tax expense. For the year ended December 31, 2018 , the Company accrued $3.9 million for the payment of interest. On July 24, 2018, the U.S. Ninth Circuit Court of Appeals overturned the U.S. Tax Court’s unanimous decision in Altera v. Commissioner, where the Tax Court held the Treasury regulation requiring participants in a qualified cost sharing arrangement share stock-based compensation costs to be invalid. On August 7, 2018, the U.S. Ninth Circuit Court of Appeals, on its own motion, withdrew its July 24, 2018 opinion to allow time for the reconstituted panel to confer. Given the increased uncertainty as to the Ninth Circuit's eventual ruling and the impact it will have on the Internal Revenue Service’s ability to challenge the technical merits of the Company's position, the Company accrued amounts for this uncertain tax position as of the year ended December 31, 2018 . The Company and one or more of its subsidiaries are subject to U.S. federal income taxes in the United States, as well as income taxes of multiple state and foreign jurisdictions. The Company is not currently under examination by the United States Internal Revenue Service. With few exceptions, the Company is generally not subject to examination for state and local income tax, or in non-U.S. jurisdictions by tax authorities for years prior to 2015 . The Company's U.S. liquidity needs are currently satisfied using cash flows generated from its U.S. operations, borrowings, or both. The Company also utilizes a variety of tax planning strategies in an effort to ensure that its worldwide cash is available in locations in which it is needed. Prior to 2017, the Company did not recognize a deferred tax liability related to undistributed foreign earnings of its subsidiaries because such earnings were considered to be indefinitely reinvested in its foreign operations, or were remitted substantially free of U.S. tax. Under the 2017 Tax Act, all foreign earnings are subject to U.S. taxation. As a result, the Company expects to repatriate a substantial portion of its foreign earnings over time, to the extent that the foreign earnings are not restricted by local laws or result in significant incremental costs associated with repatriating the foreign earnings.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION Citrix has one reportable segment. The Company's chief operating decision maker (“CODM”) reviews financial information presented on a consolidated basis for purposes of allocating resources and evaluating financial performance. The Company's CEO is the CODM. International revenues (sales outside of the United States) accounted for approximately 47.0% , 46.3% and 46.3% of the Company’s net revenues for the year ended December 31, 2018 , 2017 , and 2016 , respectively. Long-lived assets consist of property and equipment, net, and are shown below. December 31, 2018 2017 (In thousands) Property and equipment, net: United States $ 185,091 $ 189,465 United Kingdom 25,459 24,171 Other countries 32,846 39,296 Total property and equipment, net $ 243,396 $ 252,932 In fiscal year 2018 , one distributor, the Arrow Group, accounted for 14% , of the Company’s total net revenues. In fiscal year 2017 and 2016 , two distributors, Ingram Micro and Arrow, accounted for 13% and 12% , respectively, of the Company’s total net revenues. The Company’s distributor arrangements with Ingram Micro and Arrow consist of several non-exclusive, independently negotiated agreements with its subsidiaries, each of which covers different countries or regions. During 2018, the Company initiated an effort to streamline and simplify its product branding and packaging, which included naming updates to the portfolio to provide clarity on the Company's offerings and unify its sales motions. The change resulted in the Company consolidating its former Content Collaboration product group and Workspace Services product group and renaming the new product group Digital Workspace. As a result, previously reported revenue by product grouping amounts have been recast to conform to the new presentation. Revenues by product grouping were as follows for the years ended: December 31, 2018 2017 (4) 2016 (4) (In thousands) Net revenues: Digital workspace (1) $ 2,024,289 $ 1,901,952 $ 1,821,739 Networking (2) 817,193 790,434 782,875 Professional services (3) 132,421 132,300 131,466 Total net revenues $ 2,973,903 $ 2,824,686 $ 2,736,080 (1) Digital Workspace revenues are primarily comprised of sales from the Company’s application virtualization solutions, which include Citrix Virtual Apps and Desktops, the Company's unified endpoint management solutions, which include Citrix Endpoint Management, related license updates and maintenance and support, Citrix Content Collaboration, and cloud offerings. (2) Networking revenues primarily include Citrix ADC and Citrix SD-WAN, related license updates and maintenance and support and cloud offerings. (3) Professional services revenues are primarily comprised of revenues from consulting services and product training and certification services. (4) Prior period amounts have not been adjusted under the modified retrospective method of adoption of the revenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenue recognition standard. Revenues by Geographic Location The following table presents revenues by geographic location, for the years ended: December 31, 2018 2017 (1) 2016 (1) (In thousands) Net revenues: Americas $ 1,716,876 $ 1,644,008 $ 1,598,896 EMEA 956,365 888,072 863,517 APJ 300,662 292,606 273,667 Total net revenues $ 2,973,903 $ 2,824,686 $ 2,736,080 (1) As noted above, prior period amounts have not been adjusted under the modified retrospective method of adoption of the revenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenue recognition standard. Export revenue represents shipments of finished goods and services from the United States to international customers, primarily in Latin America and Canada. Shipments from the United States to international customers for 2018 , 2017 and 2016 were $141.9 million , $151.9 million and $160.5 million , respectively.

Debt

Debt	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
DEBT	DEBT Senior Notes On November 15, 2017, the Company issued $750.0 million of unsecured senior notes due December 1, 2027. The 2027 Notes accrue interest at a rate of 4.500% per annum. Interest on the 2027 Notes is due semi-annually on June 1 and December 1 of each year, beginning on June 1, 2018. The net proceeds from this offering were approximately $741.0 million , after deducting the underwriting discount and estimated offering expenses payable by the Company. Net proceeds from this offering were used to repurchase shares of the Company's common stock through an ASR transaction which the Company entered into with the ASR counterparty on November 13, 2017. The 2027 Notes will mature on December 1, 2027, unless earlier redeemed in accordance with their terms prior to such date. The Company may redeem the 2027 Notes at its option at any time in whole or from time to time in part prior to September 1, 2027 at a redemption price equal to the greater of (i) 100% of the aggregate principal amount of the 2027 Notes to be redeemed and (ii) the sum of the present values of the remaining scheduled payments under such 2027 Notes, plus in each case, accrued and unpaid interest to, but excluding, the redemption date. Among other terms, under certain circumstances, holders of the 2027 Notes may require the Company to repurchase their 2027 Notes upon the occurrence of a change of control prior to maturity for cash at a repurchase price equal to 101% of the principal amount of the 2027 Notes to be repurchased plus accrued and unpaid interest to, but excluding, the repurchase date. Credit Facility Effective January 7, 2015, the Company entered into a Credit Facility with a group of financial institutions (the “Lenders”). The Credit Facility provides for a five year revolving line of credit in the aggregate amount of $250.0 million , subject to continued covenant compliance. The Company may elect to increase the revolving credit facility by up to $250.0 million if existing or new lenders provide additional revolving commitments in accordance with the terms of the Credit Agreement. A portion of the revolving line of credit (i) in the aggregate amount of $25.0 million may be available for issuances of letters of credit and (ii) in the aggregate amount of $10.0 million may be available for swing line loans, as part of, not in addition to, the aggregate revolving commitments. The Credit Facility bears interest at LIBOR plus 1.10% and adjusts in the range of 1.00% to 1.30% above LIBOR based on the ratio of the Company’s total debt to its adjusted earnings before interest, taxes, depreciation, amortization and certain other items (“EBITDA”) as defined in the agreement. In addition, the Company is required to pay a quarterly facility fee ranging from 0.125% to 0.20% of the aggregate revolving commitments under the Credit Facility and based on the ratio of the Company’s total debt to the Company’s consolidated EBITDA. As of December 31, 2018 , there were no amounts outstanding under the Credit Facility. The Credit Agreement contains certain financial covenants that require the Company to maintain a consolidated leverage ratio of not more than 3.5 :1.0 and a consolidated interest coverage ratio of not less than 3.0 :1.0. In addition, the Credit Agreement contains customary affirmative and negative covenants, including covenants that limit or restrict the ability of the Company to grant liens, merge, dissolve or consolidate, dispose of all or substantially all of its assets, pay dividends during the existence of a default under the Credit Agreement, change its business and incur subsidiary indebtedness, in each case subject to customary exceptions for a credit facility of this size and type. The Company was in compliance with these covenants as of December 31, 2018 . Convertible Senior Notes During 2014, the Company completed a private placement of approximately $1.44 billion principal amount of 0.500% Convertible Notes due 2019. The net proceeds from this offering were approximately $1.42 billion , after deducting the initial purchasers’ discounts and commissions and the estimated offering expenses payable by the Company. The Company used approximately $82.6 million of the net proceeds to pay the cost of the Bond Hedges described below (after such cost was partially offset by the proceeds to the Company from the Warrant Transactions described below). The Company used the remainder of the net proceeds from the offering and a portion of its existing cash and investments to purchase an aggregate of approximately $1.5 billion of its common stock, as authorized under its share repurchase program. The Company purchased approximately $101.0 million of common stock from certain purchasers of the Convertible Notes in privately negotiated transactions concurrently with the closing of the offering, and purchased approximately $1.4 billion of additional shares of common stock through an ASR agreement which the Company entered into with the ASR counterparty on April 25, 2014. The Convertible Notes are governed by the terms of an indenture, dated as of April 30, 2014 (the “Indenture”), between the Company and Wilmington Trust, National Association, as trustee (the “Trustee”). The Convertible Notes are the senior unsecured obligations of the Company and bear interest at a rate of 0.500% per annum, payable semi-annually in arrears on April 15 and October 15 of each year. The Convertible Notes will mature on April 15, 2019, unless earlier repurchased or converted. Upon conversion, the Company will pay cash up to the aggregate principal amount of the Convertible Notes to be converted and deliver shares of common stock, in respect of the remainder, if any, of the Company’s conversion obligation in excess of the aggregate principal amount of the Convertible Notes being converted. In accordance with the terms of the Indenture, the conversion rate for the Convertible Notes was adjusted to 13.9510 shares of the Company's common stock per $1,000 principal amount of the Convertible Notes, which corresponds to a conversion price of $71.68 per share of common stock, as a result of a cash dividend paid in December 2018. The conversion rate is subject to adjustment from time to time upon the occurrence of certain events, including, but not limited to, the issuance of certain stock dividends on common stock, the issuance of certain rights or warrants, subdivisions, combinations, distributions of capital stock, indebtedness, or assets, the payment of cash dividends and certain issuer tender or exchange offers. The last reported sale price of the Company’s common stock for at least 20 trading days during the period of 30 consecutive trading days ending on September 30, 2018 was greater than or equal to $93.48 ( 130% of the conversion price) on each applicable trading day. As a result, each holder of the Company’s Convertible Notes had the right to convert any portion of its Convertible Notes (in minimum denominations of $1,000 in principal amount or an integral multiple thereof) during the fourth quarter of 2018. The sales price condition was also met for the quarter ended June 30, 2018. As of October 15, 2018, the Company received conversion notices from noteholders with respect to $273.0 million in aggregate principal amount of Convertible Notes requesting conversion as a result of the sales price condition having been met. Accordingly, in accordance with the terms of the Convertible Notes, in the fourth quarter of 2018 the Company made cash payments of this aggregate principal amount and delivered 1.3 million newly issued shares of its common stock in respect of the remainder of the Company's conversion obligation in excess of the aggregate principal amount of the Convertible Notes being redeemed, in full satisfaction of such converted notes. The Company received shares of its common stock under the Bond Hedges (as defined below) that offset the issuance of shares of common stock upon conversion of the Convertible Notes. See the discussion under “Convertible Note Hedge and Warrant Transaction” in this Note 13 for detailed information on the Bond Hedges. In addition, on or after October 15, 2018 until the close of business on the second scheduled trading day immediately preceding the April 15, 2019 maturity date, holders of the Convertible Notes have the right to convert their notes at any time, regardless of whether the sales price condition is met. Any conversions with respect to conversion notices received by the Company on or after October 15, 2018 will settle on the maturity date. As of December 31, 2018, the outstanding balance, net of discount, of $1.16 billion of the Convertible Notes is included in current liabilities and the difference between the face value and carrying value of $8.1 million is included in temporary equity in the accompanying consolidated balance sheets. In accounting for the settlement of the Convertible Notes, the Company allocated the fair value of the settlement consideration remitted to the noteholders between the liability and equity components. The portion of the settlement consideration allocated to the extinguishment of the liability component was based on the fair value of that component immediately before extinguishment. A loss was recognized in the consolidated statements of income for the difference between the consideration allocated to the liability component and the sum of the carrying amount of the liability component and any unamortized debt issuance costs. Additionally, upon settlement of the converted principal, the Company derecognized the related unamortized discount and issuance costs. The Company allocated the remaining settlement consideration to the reacquisition of the equity component and recognized this amount as a reduction of stockholders' equity. The Company may not redeem the Convertible Notes prior to the maturity date and no “sinking fund” is provided for the Convertible Notes, which means that the Company is not required to periodically redeem or retire the Convertible Notes. Upon the occurrence of certain fundamental changes involving the Company, holders of the Convertible Notes may require the Company to repurchase for cash all or part of their Convertible Notes in principal amounts of $1,000 or an integral multiple thereof at a repurchase price equal to 100% of the principal amount of the Convertible Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date. In accounting for the issuance of the Convertible Notes, the Company separated the Convertible Notes into liability and equity components. The carrying amount of the liability component was calculated by measuring the estimated fair value of a similar liability that does not have an associated convertible feature. The carrying amount of the equity component representing the conversion option was determined by deducting the fair value of the liability component from the face value of the Convertible Notes as a whole. The excess of the principal amount of the liability component over its carrying amount ("debt discount") is amortized to interest expense over the term of the Convertible Notes using the effective interest method with an effective interest rate of 3.0 percent per annum. The equity component is not remeasured as long as it continues to meet the conditions for equity classification. In accounting for the transaction costs related to the Convertible Note issuance, the Company allocated the total amount incurred to the liability and equity components based on their relative values. Issuance costs attributable to the $1.4 billion liability component are being amortized to expense over the term of the Convertible Notes, and issuance costs attributable to the equity component are included along with the equity component in stockholders' equity. Additionally, a deferred tax liability of $8.2 million related to a portion of the equity component transaction costs which are deductible for tax purposes is included in Other liabilities in the accompanying consolidated balance sheets. The Convertible Notes consist of the following (in thousands): December 31, 2018 December 31, 2017 Liability component Principal $ 1,164,497 $ 1,437,483 Less: note discount and issuance costs (9,052 ) (51,159 ) Net carrying amount $ 1,155,445 $ 1,386,324 Equity component Temporary equity $ 8,110 $ — Additional paid-in-capital 127,374 162,869 Total (including temporary equity) $ 135,484 $ 162,869 The following table includes total interest expense recognized related to the Convertible Notes and 2027 Notes (in thousands): Year Ended December 31, 2018 2017 2016 Contractual interest expense $ 40,151 $ 11,406 $ 7,187 Amortization of debt issuance costs 4,663 4,050 3,863 Amortization of debt discount 34,228 34,039 33,014 $ 79,042 $ 49,495 $ 44,064 See Note 6 to the Company's consolidated financial statements for fair value disclosures related to the Company's Convertible Notes and 2027 Notes. Convertible Note Hedge and Warrant Transactions In connection with the pricing of the Convertible Notes, the Company entered into convertible note hedge transactions relating to approximately 16.0 million shares of common stock (the "Bond Hedges") and also entered into separate warrant transactions (the "Warrant Transactions") with each of the Option Counterparties relating to approximately 16.0 million shares of common stock. As a result of the spin-off of its GoTo Business, the number of shares of the Company's common stock covered by the Bond Hedges and Warrant Transactions was adjusted to approximately 20.0 million shares. The Bond Hedges are generally expected to reduce the potential dilution upon conversion of the Convertible Notes and/or offset any payments in cash, shares of common stock or a combination of cash and shares of common stock, at the Company’s election, that the Company is required to make in excess of the principal amount of the Convertible Notes upon conversion of any Convertible Notes, as the case may be, in the event that the market price per share of common stock, as measured under the terms of the Bond Hedges, is greater than the strike price of the Bond Hedges, which initially corresponds to the conversion price of the Convertible Notes and is subject to anti-dilution adjustments substantially similar to those applicable to the conversion rate of the Convertible Notes. The Warrant Transactions will separately have a dilutive effect to the extent that the market value per share of common stock, as measured under the terms of the Warrant Transactions, exceeds the applicable strike price of the warrants issued pursuant to the Warrant Transactions (the “Warrants”). The strike price of the Warrants was adjusted to $94.94 as a result of the cash dividend paid in December 2018 . The Warrants will expire in ratable portions on a series of expiration dates commencing after the maturity of the Convertible Notes. The Bond Hedges and Warrants are not marked to market as the value of the Bond Hedges and Warrants were initially recorded in stockholders' equity and continue to be classified within stockholders' equity. As of December 31, 2018 , no warrants have been exercised. Aside from the initial payment of a premium to the Option Counterparties under the Bond Hedges, which amount is partially offset by the receipt of a premium under the Warrant Transactions, the Company is not required to make any cash payments to the Option Counterparties under the Bond Hedges and will not receive any proceeds if the Warrants are exercised.

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVE FINANCIAL INSTRUMENTS	DERIVATIVE FINANCIAL INSTRUMENTS Derivatives Designated as Hedging Instruments As of December 31, 2018 , the Company’s derivative assets and liabilities primarily resulted from cash flow hedges related to its forecasted operating expenses transacted in local currencies. A substantial portion of the Company’s overseas expenses are and will continue to be transacted in local currencies. To protect against fluctuations in operating expenses and the volatility of future cash flows caused by changes in currency exchange rates, the Company has established a program that uses foreign exchange forward contracts to hedge its exposure to these potential changes. The terms of these instruments, and the hedged transactions to which they relate, generally do not exceed twelve months. Generally, when the dollar is weak, foreign currency denominated expenses will be higher, and these higher expenses will be partially offset by the gains realized from the Company’s hedging contracts. Conversely, if the dollar is strong, foreign currency denominated expenses will be lower. These lower expenses will in turn be partially offset by the losses incurred from the Company’s hedging contracts. The change in the derivative component in Accumulated other comprehensive loss includes unrealized gains or losses that arose from changes in market value of the effective portion of derivatives that were held during the period, and gains or losses that were previously unrealized but have been recognized in the same line item as the forecasted transaction in current period net income due to termination or maturities of derivative contracts. This reclassification has no effect on total comprehensive income or equity. The total cumulative unrealized loss on cash flow derivative instruments was $1.0 million at December 31, 2018 , and is included in Accumulated other comprehensive loss in the accompanying consolidated balance sheets. The total cumulative unrealized gain on cash flow derivative instruments was $2.2 million at December 31, 2017 , and is included in Accumulated other comprehensive loss in the accompanying consolidated balance sheets. See Note 16 for more information related to comprehensive income. The net unrealized loss as of December 31, 2018 is expected to be recognized in income over the next 12 months at the same time the hedged items are recognized in income. Derivatives not Designated as Hedging Instruments A substantial portion of the Company’s overseas assets and liabilities are and will continue to be denominated in local currencies. To protect against fluctuations in earnings caused by changes in currency exchange rates when remeasuring the Company’s balance sheet, it utilizes foreign exchange forward contracts to hedge its exposure to this potential volatility. These contracts are not designated for hedge accounting treatment under the authoritative guidance. Accordingly, changes in the fair value of these contracts are recorded in Other (expense) income, net . Fair Values of Derivative Instruments Asset Derivatives Liability Derivatives (In thousands) December 31, 2018 December 31, 2017 December 31, 2018 December 31, 2017 Derivatives Designated as Hedging Instruments Balance Sheet Location Fair Value Balance Sheet Location Fair Value Balance Sheet Location Fair Value Balance Sheet Location Fair Value Foreign currency forward contracts Prepaid expenses and other current assets $708 Prepaid expenses and other current assets $2,481 Accrued expenses and other current liabilities $1,811 Accrued expenses and other current liabilities $110 Asset Derivatives Liability Derivatives (In thousands) December 31, 2018 December 31, 2017 December 31, 2018 December 31, 2017 Derivatives Not Designated as Hedging Instruments Balance Sheet Location Fair Value Balance Sheet Location Fair Value Balance Sheet Location Fair Value Balance Sheet Location Fair Value Foreign currency forward contracts Prepaid expenses and other current assets $56 Prepaid expenses and other current assets $17 Accrued expenses and other current liabilities $732 Accrued expenses and other current liabilities $704 The Effect of Derivative Instruments on Financial Performance For the Year ended December 31, (In thousands) Derivatives in Cash Flow Hedging Relationships Amount of (Loss) Gain Recognized in Other Location of (Loss) Gain Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion) Amount of (Loss) Gain Reclassified from 2018 2017 2018 2017 Foreign currency forward contracts $ (3,143 ) $ 5,288 Operating expenses $ (699 ) $ 758 There was no material ineffectiveness in the Company’s foreign currency hedging program in the periods presented. For the Year ended December 31, (In thousands) Derivatives Not Designated as Hedging Instruments Location of Gain (Loss) Recognized in Income on Derivative Amount of Gain (Loss) Recognized in Income on Derivative 2018 2017 Foreign currency forward contracts Other (expense) income, net $ 7,062 $ (6,804 ) Outstanding Foreign Currency Forward Contracts As of December 31, 2018 , the Company had the following net notional foreign currency forward contracts outstanding (in thousands): Foreign Currency Currency Denomination Australian dollars AUD 18,200 Brazilian Real BRL 5,500 British pounds sterling GBP 14,100 Canadian dollars CAD 2,350 Chinese renminbi CNY 41,800 Danish krone DKK 6,329 Euro EUR 9,736 Hong Kong dollars HKD 20,600 Indian rupees INR 62,000 Japanese yen JPY 2,300,000 Korean Won KRW 150,000 New Zealand Dollar NZD 100 Singapore dollars SGD 13,500 Swiss francs CHF 19,450

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
EARNINGS PER SHARE	EARNINGS PER SHARE Basic earnings per share is calculated by dividing income available to stockholders by the weighted-average number of common shares outstanding during each period. Diluted earnings per share is computed using the weighted-average number of common and dilutive common share equivalents outstanding during the period. Dilutive common share equivalents consist of shares issuable upon the exercise or settlement of stock awards and shares issuable under the employee stock purchase plan (calculated using the treasury stock method) during the period they were outstanding and potential dilutive common shares from the conversion spread on the Company’s Convertible Notes and the Company's warrants. The following table sets forth the computation of basic and diluted net income per share (in thousands, except per share information): Year Ended December 31, 2018 2017 2016 Numerator: Income from continuing operations $ 575,667 $ 21,985 $ 469,855 (Loss) income from discontinued operations, net of income taxes — (42,704 ) 66,257 Net income (loss) $ 575,667 $ (20,719 ) $ 536,112 Denominator: Denominator for basic earnings per share - weighted-average shares outstanding 136,030 150,779 155,134 Effect of dilutive employee stock awards 2,653 2,493 1,950 Effect of dilutive Convertible Notes 5,769 2,231 — Effect of dilutive warrants 1,482 — — Denominator for diluted earnings per share - weighted-average shares outstanding 145,934 155,503 157,084 Basic earnings (loss) per share: Income from continuing operations $ 4.23 $ 0.15 $ 3.03 (Loss) income from discontinued operations, net of income taxes — (0.28 ) 0.43 Basic net earnings (loss) per share $ 4.23 $ (0.13 ) $ 3.46 Diluted earnings (loss) per share: Income from continuing operations $ 3.94 $ 0.14 $ 2.99 (Loss) income from discontinued operations, net of income taxes — (0.27 ) 0.42 Diluted net earnings (loss) per share: $ 3.94 $ (0.13 ) $ 3.41 For the year ended December 31, 2018 , the weighted-average number of shares outstanding used in the computation of diluted earnings per share includes the dilutive effect of the Company's warrants, as the average stock price during the year was above the weighted-average warrant strike price of $94.94 per share. For the years ended December 31, 2017 and 2016 , the weighted-average number of shares outstanding used in the computation of diluted earnings per share does not include common stock issuable upon the exercise of the Company's warrants. The effects of these potentially issuable shares were not included in the calculation of diluted earnings per share because the effect would have been anti-dilutive. Anti-dilutive stock-based awards excluded from the calculations of diluted earnings per share were immaterial during the periods presented. The Company uses the treasury stock method for calculating any potential dilutive effect of the conversion spread on its 0.500% Convertible Notes due 2019 on diluted earnings per share, if applicable, because upon conversion the Company will pay cash up to the aggregate principal amount of the Convertible Notes to be converted and pay or deliver, as the case may be, cash, shares of common stock or a combination of cash and shares of common stock, at the Company’s election, in respect of the remainder, if any, of the Company’s conversion obligation in excess of the aggregate principal amount of the Convertible Notes being converted. The conversion spread will have a dilutive impact on diluted earnings per share when the average market price of the Company’s common stock for a given period exceeds the conversion price of $71.68 per share of common stock. For the years ended December 31, 2018 and 2017 , the average market price of the Company's common stock exceeded the conversion price, therefore, the dilutive effect of the Convertible Notes was included in the denominator of diluted earnings per share. For the year ended December 31, 2016 , the Convertible Notes have been excluded from the computation of diluted earnings per share as the effect would be anti-dilutive since the conversion price of the Convertible Notes exceeded the average market price of the Company’s common stock. See Note 13 to the Company's consolidated financial statements for detailed information on the Convertible Notes offering.

Comprehensive Income

Comprehensive Income	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
COMPREHENSIVE INCOME	COMPREHENSIVE INCOME The changes in Accumulated other comprehensive loss by component, net of tax, are as follows: Foreign currency Unrealized loss on available-for-sale securities Unrealized gain (loss) on derivative instruments Other comprehensive loss on pension liability Total (In thousands) Balance at December 31, 2017 $ (2,946 ) $ (6,666 ) $ 2,158 $ (3,352 ) $ (10,806 ) Other comprehensive (loss) income before reclassifications — (1,770 ) (3,842 ) 1,569 (4,043 ) Amounts reclassified from accumulated other comprehensive loss — 5,996 699 — 6,695 Net current period other comprehensive income (loss) — 4,226 (3,143 ) 1,569 2,652 Balance at December 31, 2018 $ (2,946 ) $ (2,440 ) $ (985 ) $ (1,783 ) $ (8,154 ) Income tax expense or benefit allocated to each component of other comprehensive income (loss) is not material. Reclassifications out of Accumulated other comprehensive loss are as follows: For the Year Ended December 31, 2018 (In thousands) Details about accumulated other comprehensive loss components Amount reclassified from Accumulated other comprehensive loss, net of tax Affected line item in the Consolidated Statements of Income Unrealized net loss on available-for-sale securities $ 5,996 Other income (expense), net Unrealized net loss on cash flow hedges 699 Operating expenses * $ 6,695 * Operating expenses amounts allocated to Research and development, Sales, marketing and services, and General and administrative are not individually significant.

Restructuring

Restructuring	12 Months Ended
	Dec. 31, 2018
Restructuring and Related Activities [Abstract]
RESTRUCTURING	RESTRUCTURING The Company has implemented multiple restructuring plans to reduce its cost structure, align resources with its product strategy and improve efficiency, which has resulted in workforce reductions and the consolidation of certain leased facilities. For the years ended December 31, 2018 , 2017 and 2016 , restructuring charges from continuing operations were comprised of the following (in thousands): Year Ended December 31, 2018 2017 2016 Employee severance and related costs $ 2,507 $ 62,844 $ 41,054 Consolidation of leased facilities 14,218 9,718 28,857 Reversal of previous charges — (187 ) (2,510 ) Total Restructuring charges $ 16,725 $ 72,375 $ 67,401 During the years ended December 31, 2018 and 2017 , the Company incurred costs of $2.5 million and $53.7 million , respectively, related to initiatives intended to accelerate the transformation to a cloud-based subscription business, increase strategic focus, and improve operational efficiency. No costs were incurred during the year ended December 31, 2016 . The majority of the activities related to this program were substantially completed by the end of 2018 . In connection with its restructuring initiatives, the Company had previously vacated or consolidated properties and subsequently reassessed its obligations on non-cancelable leases. The fair value estimate of these non-cancelable leases is based on the contractual lease costs over the remaining term, partially offset by estimated future sublease rental income. During the year ended December 31, 2018 , the Company incurred costs of $14.2 million related to the consolidation of leased facilities. During the year ended December 31, 2017 , the Company incurred costs of $8.1 million related to operational initiatives designed to improve infrastructure scalability and cost saving efficiencies. The charges primarily related to employee severance. No costs were incurred during the year ended December 31, 2016 . The charges related to employee severance were substantially completed as of the first quarter of 2018; however, the Company could continue to incur lease losses related to the consolidation of leased facilities during fiscal year 2019 . During the years ended December 31, 2017 and 2016 , the Company incurred costs of $1.9 million and $44.5 million , respectively, primarily related to its announced plan in November 2015 to simplify the Company’s enterprise go-to-market motion and roles while improving coverage, reflect changes in the Company’s product focus, and balance resources with demand across the Company’s marketing, general and administration areas. The charges are primarily related to employee severance, outplacement, professional service fees, and facility closing costs. The majority of the activities related to this program were substantially completed as of the end of the first quarter of 2016. During the years ended December 31, 2017 and 2016 , the Company recorded charges of $8.7 million and $24.0 million , respectively, related to its announced plan in January 2015 to increase strategic focus and operational efficiency. The charges primarily related to the severance and other costs directly related to the reduction of the Company's workforce and consolidation of leased facilities. The majority of the activities related to this program were substantially completed by the end of 2015. Restructuring accruals The activity in the Company’s restructuring accruals for the year ended December 31, 2018 is summarized as follows (in thousands): Total Balance at January 1, 2018 $ 55,283 Restructuring charges 16,725 Payments (26,913 ) Balance at December 31, 2018 $ 45,095 As of December 31, 2018 , the $45.1 million in outstanding restructuring accruals primarily relate to future payments for leased facilities.

Quarterly Financial Information

Quarterly Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Data [Abstract]
QUARTERLY FINANCIAL INFORMATION (UNAUDITED)	CITRIX SYSTEMS, INC. SUPPLEMENTAL FINANCIAL INFORMATION QUARTERLY FINANCIAL INFORMATION (UNAUDITED) First Quarter Second Quarter Third Quarter Fourth Quarter Total Year (In thousands, except per share amounts) 2018 Net revenues $ 697,192 $ 742,365 $ 732,476 $ 801,870 $ 2,973,903 Gross margin 588,906 633,616 628,559 689,019 2,540,100 Income from operations 165,563 145,147 164,779 202,471 677,960 Net income 144,259 106,833 158,857 165,718 575,667 Earnings per share - basic 1.04 0.79 1.18 1.24 4.23 Earnings per share - diluted 0.99 0.73 1.08 1.15 3.94 First Quarter Second Quarter Third Quarter Fourth Quarter Total Year (In thousands, except per share amounts) 2017 Net revenues $ 662,677 $ 693,227 $ 690,925 $ 777,857 $ 2,824,686 Gross margin 560,219 583,915 584,988 655,918 2,385,040 Income from continuing operations 70,325 108,829 126,720 (283,889 ) 21,985 Loss from discontinued operations, net of tax (42,704 ) — — — (42,704 ) Net income 27,621 108,829 126,720 (283,889 ) (20,719 ) Basic earnings per share: Income (loss) from continuing operations 0.46 0.72 0.84 (1.93 ) 0.15 Loss from discontinued operations (0.28 ) — — — (0.28 ) Basic earnings (loss) per share 0.18 0.72 0.84 (1.93 ) (0.13 ) Diluted earnings per share: Income (loss) from continuing operations 0.44 0.70 0.82 (1.93 ) 0.14 Loss from discontinued operations (0.27 ) — — — (0.27 ) Diluted earnings (loss) per share 0.17 0.70 0.82 (1.93 ) (0.13 ) The sum of the quarterly net income per share amounts may differ from the annual earnings per share amount due to the weighting of common and common equivalent shares outstanding during each of the respective periods.

Valuation and Qualifying Accoun

Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2018
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
VALUATION AND QUALIFYING ACCOUNTS	CITRIX SYSTEMS, INC. SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS Beginning of Period Charged to Expense Charged to Other Accounts Deductions Balance at End of Period (In thousands) 2018 Deducted from asset accounts: Allowance for doubtful accounts $ 3,420 $ 3,586 $ 457 (3) $ 3,829 (2) $ 3,634 Allowance for returns 1,225 — 1,561 (1) 1,890 (4) 896 Valuation allowance for deferred tax assets 76,789 — 8,611 (5) — 85,400 2017 Deducted from asset accounts: Allowance for doubtful accounts $ 3,889 $ 3,917 $ 9 (3) $ 4,395 (2) $ 3,420 Allowance for returns 1,994 — 4,890 (1) 5,659 (4) 1,225 Valuation allowance for deferred tax assets 14,156 — 62,633 (5) — 76,789 2016 Deducted from asset accounts: Allowance for doubtful accounts $ 6,241 $ 954 $ — $ 3,306 (2) $ 3,889 Allowance for returns 1,438 — 2,088 (1) 1,532 (4) 1,994 Valuation allowance for deferred tax assets 16,673 — (2,517 ) (5) — 14,156 (1) Charged against revenues. (2) Uncollectible accounts written off, net of recoveries. (3) Adjustments from acquisitions. (4) Credits issued for returns. (5) Related to deferred tax assets on foreign tax credits, net operating loss carryforwards, and depreciation.

Significant Accounting Polici_2

Significant Accounting Policies (Policy)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Consolidation Policy	Consolidation Policy The consolidated financial statements of the Company include the accounts of its wholly-owned subsidiaries in the Americas; Europe, the Middle East and Africa (“EMEA”); and Asia-Pacific and Japan ("APJ"). All significant transactions and balances between the Company and its subsidiaries have been eliminated in consolidation.
Recent Accounting Pronouncements	Revenue Recognition In May 2014, the Financial Accounting Standards Board issued an accounting standard update ("ASC 606") on revenue recognition. The new guidance creates a single, principle-based model for revenue recognition that expands and improves disclosures about revenue. On January 1, 2018, the Company adopted the accounting standard update for revenue from contracts with customers on a modified retrospective basis, applying the practical expedient to all contracts that the Company had not completed as of January 1, 2018. The Company elected the modified retrospective method of adoption; and consequently, results for reporting periods beginning after January 1, 2018 are presented under the new revenue standard, while prior period amounts are not adjusted and continue to be reported under the revenue accounting literature in effect during those periods. The Company recorded a net increase to retained earnings of $130.7 million as of January 1, 2018 as a result of the transition, with the impact primarily related to the cumulative effect of a decrease in deferred revenue from the upfront recognition of term licenses and the general requirement to allocate the transaction price on a relative stand-alone selling price of $99.9 million , and an increase in contract assets of $7.3 million , the cumulative effect of a decrease in commission expense of $66.4 million , partially offset by an increase from the cumulative effect of the impact on deferred income taxes of $42.9 million . The impact of adoption of ASC 606 to the Company’s consolidated statements of income and balance sheets are as follows: Year Ended December 31, 2018 As Reported Balances without adoption of ASC 606 Effect of Change Higher/(Lower) (in thousands, except per share amounts) Total net revenues $ 2,973,903 $ 2,966,848 $ 7,055 Total cost of net revenues 433,803 431,974 1,829 Gross profit 2,540,100 2,534,874 5,226 Total operating expenses 1,862,140 1,890,692 (28,552 ) Income from operations 677,960 644,182 33,778 Net income $ 575,667 $ 548,430 $ 27,237 Basic earnings per share $ 4.23 $ 4.03 $ 0.20 Diluted earnings per share $ 3.94 $ 3.76 $ 0.18 As of December 31, 2018 As Reported Balances without adoption of ASC 606 Effect of Change Higher/(Lower) (in thousands) Prepaid expenses and other current assets (1) $ 174,195 $ 147,554 $ 26,641 Other assets (2) 124,578 52,732 71,846 Deferred tax assets, net 136,998 169,064 (32,066 ) Total assets $ 5,136,049 $ 5,069,628 $ 66,421 Other liabilities (3) 148,499 135,430 13,069 Current portion of deferred revenues 1,345,243 1,413,839 (68,596 ) Long-term portion of deferred revenues 489,329 526,763 (37,434 ) Total liabilities $ 4,576,420 $ 4,669,381 $ (92,961 ) Stockholders' Equity: Retained earnings $ 4,169,019 $ 4,009,637 $ 159,382 (1) As reported primarily includes contract acquisition costs of $41.0 million . The balance without adoption of ASC 606 includes contract acquisition costs of $14.2 million . (2) As reported primarily includes contract acquisition costs of $68.2 million . (3) As reported includes deferred tax liabilities of $54.7 million . The balance without adoption of ASC 606 includes deferred tax liabilities of $56.6 million . Adoption of the standard had no impact to cash from or used in operating, financing, or investing activities on the Company’s consolidated cash flows statements. Accounting for Business Combinations In January 2017, the Financial Accounting Standards Board issued an accounting standard update on the accounting for business combinations by clarifying the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions or disposals of assets or businesses. The Company adopted the standard effective January 1, 2018. The adoption of this standard had no impact on the Company's consolidated financial position, results of operations and cash flows. Accounting for Income Taxes In October 2016, the Financial Accounting Standards Board issued an accounting standard update on the accounting for income taxes, which requires entities to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transaction occurs as opposed to deferring tax consequences and amortizing them into future periods. A modified retrospective approach with a cumulative-effect adjustment directly to retained earnings at the beginning of the period of adoption is required. The Company adopted the standard effective January 1, 2018. The adoption of this standard did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. Accounting for Investments In January 2016, the Financial Accounting Standards Board issued an accounting standard update for the recognition and measurement of financial assets and liabilities. Under the standard, equity investments that do not have readily determinable fair values and do not qualify for the net asset value practical expedient are eligible for the measurement alternative. For the Company’s equity investments in private equity securities, which do not have readily determinable fair values, the Company has elected the measurement alternative defined as cost, less impairment, plus or minus adjustments resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. For certain of the Company’s equity investments in private equity funds, the Company has elected to use the net asset value practical expedient. The guidance of this accounting standard update was adopted effective January 1, 2018. The impact of adopting the accounting standard update was not material to the consolidated financial statements. In February 2018, the Financial Accounting Standards Board issued an accounting standard update that clarified and amended some of the updates made in the January 2016 update to the recognition and measurement of financial assets and liabilities. The Company has elected to early adopt this accounting standard update effective January 1, 2018. The impact of adopting the accounting standard update was not material to the consolidated financial statements. Leases In February 2016, the Financial Accounting Standards Board issued an accounting standard update on the accounting for leases. The new guidance requires that lessees in a leasing arrangement recognize a right-of-use asset and a lease liability for most leases (other than leases that meet the definition of a short-term lease). The liability will be equal to the present value of lease payments. The asset will be based on the liability, subject to adjustment, such as for initial direct costs. The new guidance is effective for annual reporting periods beginning after December 15, 2018. Under the original guidance, the modified retrospective method of adoption was mandatory, and would have required application of the standard at the beginning of the earliest comparative period presented. However, in July 2018, the Financial Accounting Standards Board issued an update which permits entities to adopt the standard using another transition method. Under this optional transition method, the Company would recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. The Company adopted this standard effective January 1, 2019, using the optional transition method. The Company has concluded an assessment of its systems, data and processes related to the implementation of this accounting standard and has substantially completed its information technology system design and solution development. Adoption of the standard is expected to result in the recognition of additional right-of-use assets and lease liabilities for operating leases (net of previously recorded lease losses related to the consolidated leased facilities) in the range of $200.0 million to $250.0 million . The Company does not expect a material impact to its results of operations. Accounting for Cloud Computing Costs In August 2018, the Financial Accounting Standards Board issued an accounting standard update on the accounting for implementation costs incurred by customers in cloud computing arrangements that are service contracts. The new guidance aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The new guidance is effective for annual reporting periods beginning after December 15, 2019, and interim periods within those fiscal years, and early adoption is permitted. The standard can be adopted either using the prospective or retrospective transition approach. The Company will early adopt this standard on January 1, 2019 and does not expect a material impact from adoption on its consolidated financial position and results of operations. Fair Value Measurements In August 2018, the Financial Accounting Standards Board issued an accounting standard update on fair value measurements. The new guidance modifies the disclosure requirements on fair value measurements by removing certain disclosure requirements related to the fair value hierarchy, modifying existing disclosure requirements related to measurement uncertainty, and adding new disclosure requirements. The new guidance is effective for annual reporting periods beginning after December 15, 2019, and interim periods within those fiscal years, and early adoption is permitted. The adoption of this standard is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows.
Reclassifications	Reclassifications Certain reclassifications of the prior years' amounts have been made to conform to the current year's presentation. Beginning in the first quarter of fiscal year 2018, the Company revised its presentation of revenue to align with its transition to a subscription business model as follows: (1) subscription revenue, which includes revenue from the Company's cloud services offerings and on-premise subscriptions as well as revenue from its Citrix Service Provider ("CSP") offerings; (2) product and license revenue from perpetual product and license offerings; and (3) support and services revenue for perpetual product and license offerings. This change in manner of presentation did not affect the Company's total net revenues, total cost of net revenues or gross margin. Conforming changes have been made for all periods presented, as follows (in thousands): Year Ended December 31, 2017 As Previously Reported Amount Reclassified As Reported Revenues: Revenues: Software as a service $ 175,762 $ 138,973 Subscription $ 314,735 Product and licenses (1) 857,253 (90,476 ) Product and license 766,777 License updates and maintenance (2) 1,659,936 83,238 Support and services (3) 1,743,174 Professional services 131,735 (131,735 ) Total net revenues $ 2,824,686 $ — Total net revenues $ 2,824,686 Year Ended December 31, 2016 As Previously Reported Amount Reclassified As Reported Revenues: Revenues: Software as a service $ 134,682 $ 110,924 Subscription $ 245,606 Product and licenses (1) 882,898 (71,923 ) Product and license 810,975 License updates and maintenance (2) 1,587,271 92,228 Support and services (3) 1,679,499 Professional services 131,229 (131,229 ) Total net revenues $ 2,736,080 $ — Total net revenues $ 2,736,080 (1) Product and licenses as previously reported included revenue from CSPs and on-premise subscriptions that are now included in Subscription. Current period presentation only includes revenues from perpetual offerings and hardware. (2) License updates and maintenance as previously reported included revenue from CSPs and on-premise license updates and maintenance that are now included in Subscription. (3) Support and services includes revenues from license updates and maintenance from perpetual offerings as well as professional services.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Significant estimates made by management include the standalone selling price related to revenue recognition, the provision for doubtful accounts receivable, the provision to reduce obsolete or excess inventory to market, the provision for estimated returns, as well as sales allowances, the assumptions used in the valuation of stock-based awards, the assumptions used in the discounted cash flows to mark certain of its investments to market, the valuation of the Company’s goodwill, net realizable value of product related and other intangible assets, the provision for lease losses, the provision for income taxes, valuation allowance for deferred tax assets, uncertain tax positions, and the amortization and depreciation periods for contract acquisition costs, intangible and long-lived assets. While the Company believes that such estimates are fair when considered in conjunction with the consolidated financial position and results of operations taken as a whole, the actual amounts of such items, when known, will vary from these estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents at December 31, 2018 and 2017 include marketable securities, which are primarily money market funds, commercial paper, agency, and government securities, municipal securities and corporate securities with initial or remaining contractual maturities when purchased of three months or less.
Available-for-sale Investments	Available-for-sale Investments Short-term and long-term available for sale investments at December 31, 2018 and 2017 primarily consist of agency securities, corporate securities, municipal securities and government securities. Investments classified as available-for-sale are stated at fair value with unrealized gains and losses, net of taxes, reported in Accumulated other comprehensive loss. The Company classifies its available-for-sale investments as current and non-current based on their actual remaining time to maturity. The Company does not recognize changes in the fair value of its available-for-sale investments in income unless a decline in value is considered other-than-temporary in accordance with the authoritative guidance. The Company’s investment policy is designed to limit exposure to any one issuer depending on credit quality. The Company uses information provided by third parties to adjust the carrying value of certain of its investments to fair value at the end of each period. Fair values are based on a variety of inputs and may include interest rates, known historical trades, yield curve information, benchmark data, prepayment speeds, credit quality and broker/dealer quotes. See Note 5 for investment information.
Accounts Receivable	Accounts Receivable The Company’s accounts receivable are attributable primarily to direct sales to end customers via the Web and through value-added resellers, or VARs known as Citrix Solution Advisors, value-added distributors, or VADs, systems integrators, or SIs, independent software vendors, or ISVs, original equipment manufacturers, or OEMs and Citrix Service Providers, or CSPs. Collateral is generally not required. The Company also maintains allowances for doubtful accounts for estimated losses resulting from the inability of the Company’s customers to make payments which includes both general and specific reserves. The Company periodically reviews these estimated allowances by conducting an analysis of the customer's payment history and credit worthiness, the age of the trade receivable balances and current economic conditions that may affect a customer’s ability to make payments. Based on this review, the Company specifically reserves for those accounts deemed uncollectible. When receivables are determined to be uncollectible, principal amounts of such receivables outstanding are deducted from the allowance.
Inventory	Inventory Inventories are stated at the lower of cost or net realizable value on a standard cost basis, which approximates actual cost.
Contract Acquisition Costs and Revenue Recognition	Contract acquisition costs In conjunction with the adoption of the new revenue recognition standard, the Company is required to capitalize certain contract acquisition costs consisting primarily of commissions paid and related payroll taxes when contracts are signed. The asset recognized from capitalized incremental and recoverable acquisition costs is amortized on a basis consistent with the pattern of transfer of the products or services to which the asset relates and is recognized in Prepaid expenses and other current assets and Other assets in the accompanying consolidated balance sheets. The Company’s typical contracts include performance obligations related to product and licenses and support. In these contracts, incremental costs of obtaining a contract are allocated to the performance obligations based on the relative estimated standalone selling prices and then recognized on a basis that is consistent with the transfer of the goods or services to which the asset relates. The commissions paid on annual renewals of support for product and licenses are not commensurate with the initial commission. The costs allocated to product and licenses are expensed at the time of sale, when revenue for the product and functional software licenses is recognized. The costs allocated to customer support for product and licenses are amortized ratably over a period of the greater of the contract term or the average customer life, the expected period of benefit of the asset capitalized. The Company currently estimates an average customer life of two to five years, which it believes is appropriate based on consideration of the historical average customer life and the estimated useful life of the underlying product and license sold as part of the transaction. Amortization of contract acquisition costs related to support are limited to the contractual period of the arrangement as the Company intends to pay a commensurate commission upon renewal of the related support. For contracts that contain multi-year services or subscriptions, the amortization period of the capitalized costs is the expected period of benefit, which is the greater of the contractual term or the expected customer life. The Company elects to apply a practical expedient to expense contract acquisition costs as incurred where the expected period of benefit is one year or less. For the year ended on December 31, 2018, the Company recorded amortization costs of $38.1 million in relation to costs capitalized during the year, which are recorded in Sales, Marketing and Services expense in the accompanying consolidated statements of income. There was no impairment loss in relation to costs capitalized during the year ended on December 31, 2018. Revenue The following is a description of the principal activities from which the Company generates revenue. Subscription Subscription revenues primarily consist of cloud-hosted offerings which provide customers a right to use, or a right to access, one or more of the Company’s cloud-hosted subscription offerings, with routine customer support, as well as revenues from the CSP program and on-premise subscription software licenses. For the Company’s cloud-hosted performance obligations, revenue is generally recognized on a ratable basis over the contract term beginning on the date that the Company's service is made available to the customer, as the Company continuously provides online access to the web-based software that the customer can use at any time. The CSP program provides subscription-based services in which the CSP partners host software services to their end users. Product and license Product and license revenues are primarily derived from perpetual offerings related to the Company’s Digital Workspace solutions and Networking products. For performance obligations related to perpetual software license agreements, the Company determined that its licenses are functional intellectual property that are distinct as the user can benefit from the software on its own as defined under the new revenue standard. Support and services Support and services includes license updates, maintenance and professional services revenues. License updates and maintenance revenues are primarily comprised of software and hardware maintenance, when and if-available updates and technical support. For performance obligations related to license updates and maintenance, revenue is generally recognized on a straight-line basis over the period of service because the Company transfers control evenly by providing a stand-ready service. That is, the Company is continuously working on improving its products and pushing those updates through to the customer, and stands ready to provide software updates on a when and if-available basis. Services revenues are comprised of fees from consulting services primarily related to the implementation of the Company’s products and fees from product training and certification. The Company’s typical performance obligations include the following: Performance Obligation When Performance Obligation is Typically Satisfied Subscription Cloud hosted offerings Over the contract term, beginning on the date that service is made available to the customer (over time) CSP As the usage occurs (over time) On-premise subscription software licenses When software activation keys have been made available for download (point in time) Product and license Software Licenses When software activation keys have been made available for download (point in time) Hardware When control of the product passes to the customer; typically upon shipment (point in time) Support and services License updates and maintenance Ratably over the course of the service term (over time) Professional services As the services are provided (over time) Significant Judgments At contract inception, the Company assesses the solutions or services, or bundles of solutions and services, obligated in the contract with a customer to identify each performance obligation within the contract, and then evaluates whether the performance obligations are capable of being distinct and distinct within the context of the contract. Solutions and services that are not both capable of being distinct and distinct within the context of the contract are combined and treated as a single performance obligation in determining the allocation and recognition of revenue. The standalone selling price is the price at which the Company would sell a promised product or service separately to the customer. For the majority of the Company's software licenses and hardware, CSP and on-premise subscription software licenses, the Company uses the observable price in transactions with multiple performance obligations. For the majority of the Company’s support and services, and cloud-hosted subscription offerings, the Company uses the observable price when the Company sells that support and service and cloud-hosted subscription separately to similar customers. If the standalone selling price for a performance obligation is not directly observable, the Company estimates it. The Company estimates standalone selling price by taking into consideration market conditions, economics of the offering and customers’ behavior. The Company maximizes the use of observable inputs and applies estimation methods consistently in similar circumstances. The Company allocates the transaction price to each distinct performance obligation on a relative standalone selling price basis. Revenues are recognized when control of the promised products or services are transferred to customers, in an amount that reflects the consideration that the Company expects to receive in exchange for those products or services. The Company generates all of its revenues from contracts with customers. Sales tax The Company records revenue net of sales tax. Timing of revenue recognition For the Year Ended December 31, 2018 (In Thousands) Products and services transferred at a point in time $ 821,111 Products and services transferred over time 2,152,792 Total net revenues $ 2,973,903 Contract balances The Company's short-term and long-term contract assets were not significant as of December 31, 2018 . The Current portion of deferred revenues and the Long-term portion of deferred revenues were $1.25 billion and $512.8 million , respectively, as of January 1, 2018 and $1.35 billion and $489.3 million , respectively, as of December 31, 2018 . The difference in the opening and closing balances of the Company’s contract assets and liabilities primarily results from the timing difference between the Company’s performance and the customer’s payment. During the year ended December 31, 2018 , the Company recognized $1.25 billion of revenue that was included in the deferred revenue balance as of January 1, 2018. The Company performs its obligations under a contract with a customer by transferring solutions and services in exchange for consideration from the customer. Accounts receivable are recorded when the right to consideration becomes unconditional. The timing of the Company’s performance often differs from the timing of the customer’s payment, which results in the recognition of a contract asset or a contract liability. The Company recognizes a contract asset when the Company transfers products or services to a customer and the right to consideration is conditional on something other than the passage of time. The Company recognizes a contract liability when it has received consideration or an amount of consideration is due from the customer and the Company has a future obligation to transfer products or services. The Company had no asset impairment charges related to contract assets as of December 31, 2018 . For the Company’s software and hardware products, the timing of payment is typically upfront for its perpetual offerings and the Company’s on-premise subscriptions. Therefore, deferred revenue is created when a contract includes performance obligations such as license updates and maintenance or certain professional services that are satisfied over time. For subscription contracts, the timing of payment is typically in advance of services, and deferred revenue is created as these services are provided over time. A significant portion of the Company’s contracts have an original duration of one year or less; therefore, the Company applies a practical expedient to determine whether a significant financing component exists and does not consider the effects of the time value of money. For multi-year contracts, the Company bills annually. Transaction price allocated to the remaining performance obligations The following table includes estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied or partially unsatisfied at the end of the reporting period (in thousands): <1-3 years 3-5 years 5 years or more Total Subscription $ 431,527 $ 45,790 $ 535 $ 477,852 Support and services 1,637,387 55,738 2,059 1,695,184 Total net revenues $ 2,068,914 $ 101,528 $ 2,594 $ 2,173,036 Cost of Net Revenues Cost of subscription, support and services revenues consists primarily of compensation and other personnel-related costs of providing technical support, consulting, cloud capacity costs, as well as the costs related to providing the Company's offerings delivered via the cloud. Cost of product and license revenues consists primarily of hardware, royalties, product media and duplication, manuals, shipping expense, and packaging materials. In addition, the Company is a party to licensing agreements with various entities, which give the Company the right to use certain software code in its solutions or in the development of future solutions in exchange for the payment of fixed fees or amounts based upon the sales of the related product. The licensing agreements generally have terms ranging from one to five years, and generally include renewal options. However, some agreements are perpetual unless expressly terminated. Royalties and other costs related to these agreements are also included in Cost of net revenues. Also included in Cost of net revenues is amortization and impairment of product related intangible assets.
Derivatives and Hedging Activities	Derivatives and Hedging Activities In accordance with the authoritative guidance, the Company records derivatives at fair value as either assets or liabilities on the balance sheet. For derivatives that are designated as and qualify as effective cash flow hedges, the portion of gain or loss on the derivative instrument effective at offsetting changes in the hedged item is reported as a component of Accumulated other comprehensive loss and reclassified into earnings as operating expense, net, when the hedged transaction affects earnings. Derivatives not designated as hedging instruments are adjusted to fair value through earnings as Other (expense) income, net , in the period during which changes in fair value occur. The application of the authoritative guidance could impact the volatility of earnings. The Company formally documents all relationships between hedging instruments and hedged items, as well as its risk-management objective and strategy for undertaking various hedge transactions. This process includes attributing all derivatives that are designated as cash flow hedges to floating rate assets or liabilities or forecasted transactions. The Company also formally assesses, both at the inception of the hedge and on an ongoing basis, whether each derivative is highly effective in offsetting changes in cash flows of the hedged item. Fluctuations in the value of the derivative instruments are generally offset by changes in the hedged item; however, if it is determined that a derivative is not highly effective as a hedge or if a derivative ceases to be a highly effective hedge, the Company will discontinue hedge accounting prospectively for the affected derivative. The Company is exposed to risk of default by its hedging counterparties. Although this risk is concentrated among a limited number of counterparties, the Company’s foreign exchange hedging policy attempts to minimize this risk by placing limits on the amount of exposure that may exist with any single financial institution at a time.
Property and Equipment	Property and Equipment Property and equipment is stated at cost. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, which is generally three years for computer equipment and software; the lesser of the lease term or ten years for leasehold improvements, which is the estimated useful life; seven years for office equipment and furniture and the Company’s enterprise resource planning systems; and 40 years for buildings.
Long-Lived Assets	Long-Lived Assets The Company reviews for impairment of long-lived assets and certain identifiable intangible assets to be held and used whenever events or changes in circumstances indicate that the carrying amount of such assets may not be fully recoverable. Determination of recoverability is based on an estimate of undiscounted future cash flows resulting from the use of the asset and its eventual disposition. Measurement of an impairment loss is based on the fair value of the asset compared to its carrying value. Long-lived assets and certain identifiable intangible assets to be disposed of are reported at the lower of carrying amount or fair value less costs to sell.
Goodwill	Goodwill The Company accounts for goodwill in accordance with the authoritative guidance, which requires that goodwill and certain intangible assets are not amortized, but are subject to an annual impairment test. During 2018, the Company initiated an effort to streamline and simplify its product branding and packaging, which included naming updates to the portfolio to provide clarity on the Company's offerings and unify its sales motions. The change resulted in the Company consolidating its Content Collaboration product group with Workspace Services and renaming the new product group Digital Workspace. As a result, the Company's two reporting units (Enterprise and Service Provider and Content Collaboration) were combined into one , consistent with how management reviews the operating results of the business. In connection with this change, the Company performed a qualitative goodwill assessment of the reporting units and determined there were no indicators of impairment during the third quarter of 2018. The change in reporting units did not result in a reallocation of goodwill or a change in reportable segments. In addition, there was no impairment of goodwill or indefinite lived intangible assets as a result of the annual impairment analysis completed during the fourth quarters of 2018 and 2017. See Note 4 for more information regarding the Company's acquisitions
Intangible Assets	Intangible Assets The Company has intangible assets which were primarily acquired in conjunction with business combinations and technology purchases. Intangible assets with finite lives are recorded at cost, less accumulated amortization. Amortization is computed over the estimated useful lives of the respective assets, generally three to seven years, except for patents, which are amortized over the lesser of their remaining life or ten years. In-process R&D is initially capitalized at fair value as an intangible asset with an indefinite life and assessed for impairment thereafter. When in-process R&D projects are completed, the corresponding amount is reclassified as an amortizable intangible asset and is amortized over the asset's estimated useful life.
Software Development Costs	Software Development Costs The authoritative guidance requires certain internal software development costs related to software to be sold to be capitalized upon the establishment of technological feasibility. The Company's software development costs incurred subsequent to achieving technological feasibility have not been significant and substantially all software development costs have been expensed as incurred.
Internal Use Software	Internal Use Software In accordance with the authoritative guidance, the Company capitalizes external direct costs of materials and services and internal costs such as payroll and benefits of those employees directly associated with the development of new functionality in internal use software. The amount of costs capitalized during the years ended 2018 and 2017 relating to internal use software was $14.8 million and $41.5 million , respectively. These costs are being amortized over the estimated useful life of the software, which is generally three to seven years, and are included in property and equipment in the accompanying consolidated balance sheets.
Pension Liability	Pension Liability The Company provides retirement benefits to certain employees who are not U.S. based. Generally, benefits under these programs are based on an employee’s length of service and level of compensation. The majority of these programs are commonly referred to as termination indemnities, which provide retirement benefits in accordance with programs mandated by the governments of the countries in which such employees work.
Product Concentration	Product Concentration The Company derives a substantial portion of its revenues from its Digital Workspace solutions, which include its Citrix Virtual Apps and Desktops solutions and related services, and anticipates that these solutions and future derivative solutions and product lines based upon this technology will continue to constitute a majority of its revenue. The Company could experience declines in demand for its Digital Workspace solutions and other solutions, whether as a result of general economic conditions, the delay or reduction in technology purchases, new competitive product releases, price competition, and lack of success of its strategic partners, technological change or other factors. Additionally, the Company's Networking products generate revenues from a limited number of customers. As a result, if the Networking product grouping loses certain customers or one or more such customers significantly decreases its orders, the Company's business, results of operations and financial condition could be adversely affected.
Foreign Currency	Foreign Currency The functional currency for all of the Company’s wholly-owned foreign subsidiaries is the U.S. dollar. Monetary assets and liabilities of such subsidiaries are remeasured into U.S. dollars at exchange rates in effect at the balance sheet date, and revenues and expenses are remeasured at average rates prevailing during the year. Foreign currency transaction gains and losses are the result of exchange rate changes on transactions denominated in currencies other than the functional currency, including U.S. dollars. The remeasurement of those foreign currency transactions is included in determining net income or loss for the period of exchange.
Advertising Costs	Advertising Costs The Company expenses advertising costs as incurred. The Company has advertising agreements with, and purchases advertising from, online media providers to advertise its solutions. The Company also has cooperative advertising agreements with certain distributors and resellers whereby the Company will reimburse distributors and resellers for qualified advertising of Company solutions. Reimbursement is made once the distributor, reseller or provider provides substantiation of qualified expenses. The Company estimates the impact of these expenses and recognizes them at the time of product sales as a reduction of net revenue in the accompanying consolidated statements of income.
Income Taxes	Income Taxes The Company and one or more of its subsidiaries are subject to U.S. federal income taxes in the United States, as well as income taxes of multiple state and foreign jurisdictions. The Company is not currently under examination by the United States Internal Revenue Service. With few exceptions, the Company is generally not subject to examination for state and local income tax, or in non-U.S. jurisdictions by tax authorities for years prior to 2015 . In the ordinary course of global business, there are transactions for which the ultimate tax outcome is uncertain; thus, judgment is required in determining the worldwide provision for income taxes. The Company provides for income taxes on transactions based on its estimate of the probable liability. The Company adjusts its provision as appropriate for changes that impact its underlying judgments. Changes that impact provision estimates include such items as jurisdictional interpretations on tax filing positions based on the results of tax audits and general tax authority rulings. Due to the evolving nature of tax rules combined with the large number of jurisdictions in which the Company operates, estimates of its tax liability and the realizability of its deferred tax assets could change in the future, which may result in additional tax liabilities and adversely affect the Company’s results of operations, financial condition and cash flows. The Company is required to estimate its income taxes in each of the jurisdictions in which it operates as part of the process of preparing its consolidated financial statements. The authoritative guidance requires a valuation allowance to reduce the deferred tax assets reported if, based on the weight of the evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. The Company reviews deferred tax assets periodically for recoverability and makes estimates and judgments regarding the expected geographic sources of taxable income and gains from investments, as well as tax planning strategies in assessing the need for a valuation allowance.
Accounting for Stock-Based Compensation Plans	Accounting for Stock-Based Compensation Plans The Company has various stock-based compensation plans for its employees and outside directors and accounts for stock-based compensation arrangements in accordance with the authoritative guidance, which requires the Company to measure and record compensation expense in its consolidated financial statements using a fair value method.
Earnings Per Share	Earnings per Share Basic earnings per share is calculated by dividing income available to stockholders by the weighted-average number of common shares outstanding during each period. Diluted earnings per share is computed using the weighted-average number of common and dilutive common share equivalents outstanding during the period. Dilutive common share equivalents consist of shares issuable upon the exercise or settlement of stock awards and shares issuable under the employee stock purchase plan (calculated using the treasury stock method) during the period they were outstanding and potential dilutive common shares from the conversion spread on the Company’s Convertible Notes and the Company's warrants. During the years ended December 31, 2017 and December 31, 2016 , the computation of diluted earnings per share does not include common stock issuable upon the exercise of the Company's warrants because the effect would have been anti-dilutive.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	The impact of adoption of ASC 606 to the Company’s consolidated statements of income and balance sheets are as follows: Year Ended December 31, 2018 As Reported Balances without adoption of ASC 606 Effect of Change Higher/(Lower) (in thousands, except per share amounts) Total net revenues $ 2,973,903 $ 2,966,848 $ 7,055 Total cost of net revenues 433,803 431,974 1,829 Gross profit 2,540,100 2,534,874 5,226 Total operating expenses 1,862,140 1,890,692 (28,552 ) Income from operations 677,960 644,182 33,778 Net income $ 575,667 $ 548,430 $ 27,237 Basic earnings per share $ 4.23 $ 4.03 $ 0.20 Diluted earnings per share $ 3.94 $ 3.76 $ 0.18 As of December 31, 2018 As Reported Balances without adoption of ASC 606 Effect of Change Higher/(Lower) (in thousands) Prepaid expenses and other current assets (1) $ 174,195 $ 147,554 $ 26,641 Other assets (2) 124,578 52,732 71,846 Deferred tax assets, net 136,998 169,064 (32,066 ) Total assets $ 5,136,049 $ 5,069,628 $ 66,421 Other liabilities (3) 148,499 135,430 13,069 Current portion of deferred revenues 1,345,243 1,413,839 (68,596 ) Long-term portion of deferred revenues 489,329 526,763 (37,434 ) Total liabilities $ 4,576,420 $ 4,669,381 $ (92,961 ) Stockholders' Equity: Retained earnings $ 4,169,019 $ 4,009,637 $ 159,382 (1) As reported primarily includes contract acquisition costs of $41.0 million . The balance without adoption of ASC 606 includes contract acquisition costs of $14.2 million . (2) As reported primarily includes contract acquisition costs of $68.2 million . (3) As reported includes deferred tax liabilities of $54.7 million . The balance without adoption of ASC 606 includes deferred tax liabilities of $56.6 million .
Schedule of Reclassifications	This change in manner of presentation did not affect the Company's total net revenues, total cost of net revenues or gross margin. Conforming changes have been made for all periods presented, as follows (in thousands): Year Ended December 31, 2017 As Previously Reported Amount Reclassified As Reported Revenues: Revenues: Software as a service $ 175,762 $ 138,973 Subscription $ 314,735 Product and licenses (1) 857,253 (90,476 ) Product and license 766,777 License updates and maintenance (2) 1,659,936 83,238 Support and services (3) 1,743,174 Professional services 131,735 (131,735 ) Total net revenues $ 2,824,686 $ — Total net revenues $ 2,824,686 Year Ended December 31, 2016 As Previously Reported Amount Reclassified As Reported Revenues: Revenues: Software as a service $ 134,682 $ 110,924 Subscription $ 245,606 Product and licenses (1) 882,898 (71,923 ) Product and license 810,975 License updates and maintenance (2) 1,587,271 92,228 Support and services (3) 1,679,499 Professional services 131,229 (131,229 ) Total net revenues $ 2,736,080 $ — Total net revenues $ 2,736,080 (1) Product and licenses as previously reported included revenue from CSPs and on-premise subscriptions that are now included in Subscription. Current period presentation only includes revenues from perpetual offerings and hardware. (2) License updates and maintenance as previously reported included revenue from CSPs and on-premise license updates and maintenance that are now included in Subscription. (3) Support and services includes revenues from license updates and maintenance from perpetual offerings as well as professional services.
Schedule of Property and Equipment	Property and equipment consist of the following: December 31, 2018 2017 (In thousands) Buildings $ 76,152 $ 76,152 Computer equipment 189,333 176,140 Software 433,033 388,583 Equipment and furniture 78,401 73,700 Leasehold improvements 182,848 168,656 959,767 883,231 Less: accumulated depreciation and amortization (741,587 ) (675,892 ) Assets under construction 8,447 28,824 Land 16,769 16,769 Total $ 243,396 $ 252,932
Schedule of Changes in Goodwill	The following table presents the change in goodwill during 2018 and 2017 (in thousands): Balance at January 1, 2018 Additions Other Balance at December 31, 2018 Balance at January 1, 2017 Additions Other Balance at December 31, 2017 Goodwill $ 1,614,494 $ 188,176 (1) $ — $ 1,802,670 $ 1,585,893 $ 28,601 (2) $ — $ 1,614,494 (1) Amount relates to preliminary purchase price allocation of goodwill associated with the 2018 business combinations. See Note 4 for more information regarding the Company's acquisitions. (2) Amount relates to the purchase price allocation of goodwill associated with the 2017 business combination. See Note 4 for more information regarding the Company's acquisitions.
Schedule of Intangible Assets	Intangible assets consist of the following (in thousands): December 31, 2018 Gross Carrying Amount Accumulated Amortization Weighted-Average Life (Years) Product related intangible assets $ 746,152 $ 601,993 6.06 Other 227,922 204,894 6.40 Total $ 974,074 $ 806,887 6.14 December 31, 2017 Gross Carrying Amount Accumulated Amortization Weighted-Average Life (Years) Product related intangible assets $ 663,004 $ 554,934 6.10 Other 222,923 189,041 6.49 Total $ 885,927 $ 743,975 6.20
Schedule of Estimated Future Annual Amortization Expense of Intangible Assets	Estimated future amortization expense of intangible assets with finite lives as of December 31, 2018 is as follows (in thousands): Year ending December 31, 2019 $ 50,981 2020 38,482 2021 24,494 2022 22,644 2023 19,292 Thereafter 11,294 Total $ 167,187
Disaggregation of Revenue	Timing of revenue recognition For the Year Ended December 31, 2018 (In Thousands) Products and services transferred at a point in time $ 821,111 Products and services transferred over time 2,152,792 Total net revenues $ 2,973,903
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction	The following table includes estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied or partially unsatisfied at the end of the reporting period (in thousands): <1-3 years 3-5 years 5 years or more Total Subscription $ 431,527 $ 45,790 $ 535 $ 477,852 Support and services 1,637,387 55,738 2,059 1,695,184 Total net revenues $ 2,068,914 $ 101,528 $ 2,594 $ 2,173,036

Discontinued Operations (Tables

Discontinued Operations (Tables)	12 Months Ended
	Dec. 31, 2018
Discontinued Operations and Disposal Groups [Abstract]
Schedule of Discontinued Operations	The following table presents the financial results of the GoTo Business through the date of the Spin-off for the indicated periods and do not include corporate overhead allocations: 2017 2016 (in thousands) Net revenues $ 58,215 $ 682,185 Cost of net revenues 15,456 154,652 Gross margin 42,759 527,533 Operating expenses: Research and development 9,108 93,892 Sales, marketing and services 20,881 209,475 General and administrative 7,636 63,270 Amortization of other intangible assets 1,176 14,097 Restructuring 3,189 3,721 Separation 40,573 54,084 Total operating expenses 82,563 438,539 (Loss) income from discontinued operations before income taxes (39,804 ) 88,994 Income tax expense 2,900 22,737 (Loss) income from discontinued operations, net of income tax $ (42,704 ) $ 66,257

Acquisition (Tables)

Acquisition (Tables)	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Schedule of Allocation of Purchase Price	The allocation of the total purchase prices is summarized below (in thousands): Sapho Cedexis Purchase Price Allocation Asset Life Purchase Price Allocation Asset Life Current assets $ 4,671 $ 8,961 Intangible assets 53,600 5 years 27,200 1-6 years Goodwill 144,173 Indefinite 44,003 Indefinite Deferred taxes — 3,173 Other assets — 69 Assets acquired 202,444 83,406 Current liabilities assumed 3,323 5,711 Assumed debt — 5,674 Other long term liabilities assumed 370 — Deferred taxes 12,094 — Net assets acquired $ 186,657 $ 72,021
Schedule of Intangible Assets Acquired	Identifiable intangible assets acquired in connection with the 2018 Business Combinations (in thousands) and the weighted-average lives are as follows: Sapho Asset Life Cedexis Asset Life Customer relationships $ 1,600 5 years $ 2,000 1 year Developed technology 52,000 5 years 23,800 5-6 years Tradenames — 1,400 1 year Total $ 53,600 $ 27,200
Schedule of Pro-Forma Information	The following unaudited pro-forma information combines the consolidated results of the operations of the Company and the 2018 Business Combinations as if the acquisitions had occurred on January 1, 2017, the first day of the Company’s fiscal year 2017 (in thousands): Twelve Months Ended December 31 2018 2017 Revenues $ 2,977,155 $ 2,838,880 Income from continuing operations 651,047 530,470 Net income (loss) 550,985 (56,601 )

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Schedule of Available-for-sale Securities	Investments in available-for-sale securities at fair value were as follows for the periods ended (in thousands): December 31, 2018 December 31, 2017 Description of the Securities Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Agency securities $ 314,982 $ 333 $ (2,367 ) $ 312,948 $ 441,315 $ 509 $ (2,760 ) $ 439,064 Corporate securities 612,698 116 (4,156 ) 608,658 810,444 268 (3,020 ) 807,692 Municipal securities 2,500 4 — 2,504 3,965 2 (2 ) 3,965 Government securities 234,668 91 (935 ) 233,824 367,595 44 (1,516 ) 366,123 Total $ 1,164,848 $ 544 $ (7,458 ) $ 1,157,934 $ 1,623,319 $ 823 $ (7,298 ) $ 1,616,844

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Assets And Liabilities Measured At Fair Value On A Recurring Basis	Assets and Liabilities Measured at Fair Value on a Recurring Basis As of December 31, 2018 Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (in thousands) Assets: Cash and cash equivalents: Cash $ 505,363 $ 505,363 $ — $ — Money market funds 88,126 88,126 — — Agency securities 3,296 — 3,296 — Corporate securities 9,371 — 9,371 — Government securities 12,610 12,610 — Available-for-sale securities: Agency securities 312,948 — 312,948 — Corporate securities 608,658 — 607,945 713 Municipal securities 2,504 — 2,504 — Government securities 233,824 — 233,824 — Prepaid expenses and other current assets: Foreign currency derivatives 764 — 764 — Total assets $ 1,777,464 $ 593,489 $ 1,183,262 $ 713 Accrued expenses and other current liabilities: Foreign currency derivatives 2,543 — 2,543 — Total liabilities $ 2,543 $ — $ 2,543 $ — As of December 31, 2017 Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (in thousands) Assets: Cash and cash equivalents: Cash $ 556,520 $ 556,520 $ — $ — Money market funds 555,826 555,826 — — Corporate securities 2,784 — 2,784 — Available-for-sale securities: Agency securities 439,064 — 439,064 — Corporate securities 807,692 — 807,299 393 Municipal securities 3,965 — 3,965 — Government securities 366,123 — 366,123 — Prepaid expenses and other current assets: Foreign currency derivatives 2,498 — 2,498 — Total assets $ 2,734,472 $ 1,112,346 $ 1,621,733 $ 393 Accrued expenses and other current liabilities: Foreign currency derivatives 814 — 814 — Total liabilities $ 814 $ — $ 814 $ —
Fair Value, by Balance Sheet Grouping	As of December 31, 2018 , the fair value of the 2027 Notes and Convertible Notes, which was determined based on inputs that are observable in the market (Level 2), based on the closing trading price per $100 as of the last day of trading for the year ended December 31, 2018 , and carrying value of debt instruments (carrying value excludes the equity component of the Company’s Convertible Notes classified in equity) was as follows (in thousands): Fair Value Carrying Value 2027 Notes $ 717,375 $ 741,825 Convertible Senior Notes $ 1,648,567 $ 1,155,445

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2018
Accounts Payable and Accrued Liabilities, Current [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses consist of the following: December 31, 2018 2017 (In thousands) Accrued compensation and employee benefits $ 196,847 $ 161,049 Other accrued expenses 93,645 116,630 Total $ 290,492 $ 277,679

Employee Stock-Based Compensa_2

Employee Stock-Based Compensation and Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Assumptions Used To Value Option Grants	The Company used the Black-Scholes model to estimate the fair value of the 2015 ESPP awards with the following weighted-average assumptions: Year Ended Year Ended Year Ended December 31, 2018 December 31, 2017 December 31, 2016 Expected volatility factor 0.26 - 0.29 0.27 - 0.29 0.27 - 0.41 Risk free interest rate 1.12% - 2.19% 0.60% - 1.12% 0.25% - 0.42% Expected dividend yield 0% - 1.27% 0 % 0 % Expected life (in years) 0.5 0.5 0.5
Detail Of The Total Stock-Based Compensation Recognized By Income Statement Classification	The detail of the total stock-based compensation recognized by income statement classification is as follows (in thousands): Income Statement Classifications 2018 2017 2016 Cost of subscription, support and services $ 7,979 $ 4,281 $ 2,179 Research and development 66,154 47,291 38,578 Sales, marketing and services 72,406 55,173 48,514 General and administrative 57,080 58,375 63,468 Total $ 203,619 $ 165,120 $ 152,739
Schedule of Nonvested Stock Unit Activity	The following table summarizes the Company's non-vested stock unit activity for the year ended December 31, 2018 : Number of Shares Weighted- Average Fair Value at Grant Date Non-vested stock units at December 31, 2017 4,622,546 $ 82.83 Granted 3,903,225 92.20 Vested (2,076,052 ) 71.92 Forfeited (596,218 ) 74.07 Non-vested stock units at December 31, 2018 5,853,501 88.79
Non-vested stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Assumptions Used To Value Option Grants	The grant date fair value of the non-vested performance stock unit awards was determined through the use of a Monte Carlo simulation model, which utilized multiple input variables that determined the probability of satisfying the market condition requirements applicable to each award as follows: March 2017 Grant (Modified) March 2017 Grant March 2016 Grant January 2016 Grant Expected volatility factor 0.16 - 0.32 0.27 - 0.32 0.29 - 0.39 0.29 - 0.37 Risk free interest rate 2.67 % 1.48 % 0.91 % 1.10 % Expected dividend yield 0 % 0 % 0 % 0 %

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of Lease Commitments	Lease commitments under non-cancelable operating leases with initial or remaining terms in excess of one year and sublease income associated with non-cancelable subleases, are as follows: Operating Leases Sublease Income (In thousands) Years ending December 31, 2019 $ 57,122 $ 241 2020 49,358 — 2021 39,981 — 2022 35,296 — 2023 32,018 — Thereafter 87,621 — Total $ 301,396 $ 241

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
United States and Foreign Components of Income Before Income Taxes	The United States and foreign components of income before income taxes are as follows: 2018 2017 2016 (In thousands) United States $ 174,519 $ 78,897 $ 59,344 Foreign 454,936 471,449 468,426 Total $ 629,455 $ 550,346 $ 527,770
Components of the Provision for Income Taxes	The components of the provision for income taxes are as follows: 2018 2017 2016 (In thousands) Current: Federal $ (19,461 ) $ 374,602 $ 18,832 Foreign 70,146 56,526 52,978 State 16,259 3,075 7,759 Total current 66,944 434,203 79,569 Deferred: Federal 1,899 52,842 (7,688 ) Foreign (14,804 ) (5,468 ) (3,139 ) State (251 ) 46,784 (10,827 ) Total deferred (13,156 ) 94,158 (21,654 ) Total provision $ 53,788 $ 528,361 $ 57,915
Components of Deferred Tax Assets and Liabilities	The following table presents the breakdown of net deferred tax assets: December 31, 2018 2017 (In thousands) Deferred tax assets $ 136,998 $ 152,362 Deferred tax liabilities (15,075 ) (237 ) Total net deferred tax assets $ 121,923 $ 152,125 The significant components of the Company’s deferred tax assets and liabilities consisted of the following: December 31, 2018 2017 (In thousands) Deferred tax assets: Accruals and reserves $ 27,022 $ 30,317 Deferred revenue 62,085 65,016 Tax credits 81,720 80,772 Net operating losses 54,747 36,674 Stock based compensation 30,936 21,714 Depreciation and amortization — 4,939 Valuation allowance (85,400 ) (76,789 ) Total deferred tax assets 171,110 162,643 Deferred tax liabilities: Acquired technology (15,681 ) (2,882 ) Depreciation and amortization (5,044 ) — Prepaid expenses (23,213 ) (7,414 ) Other (5,249 ) (222 ) Total deferred tax liabilities (49,187 ) (10,518 ) Total net deferred tax assets $ 121,923 $ 152,125
Reconciliation of The Company's Effective Tax Rate to The Statutory Federal Rate	A reconciliation of the Company’s effective tax rate to the statutory federal rate is as follows: Year Ended December 31, 2018 2017 2016 Federal statutory taxes 21.0 % 35.0 % 35.0 % State income taxes, net of federal tax benefit 0.7 2.1 0.8 Foreign operations (5.4 ) (20.0 ) (21.6 ) Permanent differences 2.0 2.6 3.2 The 2017 Tax Act - tax rate impact on deferred taxes (0.7 ) 11.8 — The 2017 Tax Act - transition tax (3.5 ) 66.3 — Change in valuation allowance reserve 0.4 8.8 — Change in deferred tax liability related to acquired intangibles (0.1 ) 0.3 (0.8 ) Tax credits (5.8 ) (7.6 ) (7.9 ) Stock-based compensation (1.9 ) (3.6 ) 0.3 Change in accruals for uncertain tax positions 1.8 0.3 2.2 Other — — (0.2 ) 8.5 % 96.0 % 11.0 %
Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits for the years ended December 31, 2018 and 2017 is as follows (in thousands): Balance at December 31, 2016 $ 69,801 Additions based on tax positions related to the current year 9,293 Additions for tax positions of prior years 7,656 Reductions related to audit settlements (137 ) Reductions related to the expiration of statutes of limitations (8,764 ) Balance at December 31, 2017 77,849 Additions based on tax positions related to the current year 10,168 Additions for tax positions of prior years 10,325 Reductions related to the expiration of statutes of limitations (8,436 ) Balance at December 31, 2018 $ 89,906

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Identifiable and Long-Lived Assets by Product Grouping and Countries	Long-lived assets consist of property and equipment, net, and are shown below. December 31, 2018 2017 (In thousands) Property and equipment, net: United States $ 185,091 $ 189,465 United Kingdom 25,459 24,171 Other countries 32,846 39,296 Total property and equipment, net $ 243,396 $ 252,932
Revenues By Product Grouping	Revenues by product grouping were as follows for the years ended: December 31, 2018 2017 (4) 2016 (4) (In thousands) Net revenues: Digital workspace (1) $ 2,024,289 $ 1,901,952 $ 1,821,739 Networking (2) 817,193 790,434 782,875 Professional services (3) 132,421 132,300 131,466 Total net revenues $ 2,973,903 $ 2,824,686 $ 2,736,080 (1) Digital Workspace revenues are primarily comprised of sales from the Company’s application virtualization solutions, which include Citrix Virtual Apps and Desktops, the Company's unified endpoint management solutions, which include Citrix Endpoint Management, related license updates and maintenance and support, Citrix Content Collaboration, and cloud offerings. (2) Networking revenues primarily include Citrix ADC and Citrix SD-WAN, related license updates and maintenance and support and cloud offerings. (3) Professional services revenues are primarily comprised of revenues from consulting services and product training and certification services. (4) Prior period amounts have not been adjusted under the modified retrospective method of adoption of the revenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenue recognition standard.
Revenues By Geographic Location	The following table presents revenues by geographic location, for the years ended: December 31, 2018 2017 (1) 2016 (1) (In thousands) Net revenues: Americas $ 1,716,876 $ 1,644,008 $ 1,598,896 EMEA 956,365 888,072 863,517 APJ 300,662 292,606 273,667 Total net revenues $ 2,973,903 $ 2,824,686 $ 2,736,080 (1) As noted above, prior period amounts have not been adjusted under the modified retrospective method of adoption of the revenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenue recognition standard.

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Convertible Debt	The Convertible Notes consist of the following (in thousands): December 31, 2018 December 31, 2017 Liability component Principal $ 1,164,497 $ 1,437,483 Less: note discount and issuance costs (9,052 ) (51,159 ) Net carrying amount $ 1,155,445 $ 1,386,324 Equity component Temporary equity $ 8,110 $ — Additional paid-in-capital 127,374 162,869 Total (including temporary equity) $ 135,484 $ 162,869
Schedule of Interest Expense Recognized Related to Convertible Notes	The following table includes total interest expense recognized related to the Convertible Notes and 2027 Notes (in thousands): Year Ended December 31, 2018 2017 2016 Contractual interest expense $ 40,151 $ 11,406 $ 7,187 Amortization of debt issuance costs 4,663 4,050 3,863 Amortization of debt discount 34,228 34,039 33,014 $ 79,042 $ 49,495 $ 44,064

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of the Fair Values of Derivative Instruments	Fair Values of Derivative Instruments Asset Derivatives Liability Derivatives (In thousands) December 31, 2018 December 31, 2017 December 31, 2018 December 31, 2017 Derivatives Designated as Hedging Instruments Balance Sheet Location Fair Value Balance Sheet Location Fair Value Balance Sheet Location Fair Value Balance Sheet Location Fair Value Foreign currency forward contracts Prepaid expenses and other current assets $708 Prepaid expenses and other current assets $2,481 Accrued expenses and other current liabilities $1,811 Accrued expenses and other current liabilities $110 Asset Derivatives Liability Derivatives (In thousands) December 31, 2018 December 31, 2017 December 31, 2018 December 31, 2017 Derivatives Not Designated as Hedging Instruments Balance Sheet Location Fair Value Balance Sheet Location Fair Value Balance Sheet Location Fair Value Balance Sheet Location Fair Value Foreign currency forward contracts Prepaid expenses and other current assets $56 Prepaid expenses and other current assets $17 Accrued expenses and other current liabilities $732 Accrued expenses and other current liabilities $704
Schedule of Effect of Derivative Instruments on Financial Performance	The Effect of Derivative Instruments on Financial Performance For the Year ended December 31, (In thousands) Derivatives in Cash Flow Hedging Relationships Amount of (Loss) Gain Recognized in Other Location of (Loss) Gain Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion) Amount of (Loss) Gain Reclassified from 2018 2017 2018 2017 Foreign currency forward contracts $ (3,143 ) $ 5,288 Operating expenses $ (699 ) $ 758 For the Year ended December 31, (In thousands) Derivatives Not Designated as Hedging Instruments Location of Gain (Loss) Recognized in Income on Derivative Amount of Gain (Loss) Recognized in Income on Derivative 2018 2017 Foreign currency forward contracts Other (expense) income, net $ 7,062 $ (6,804 )
Currency Forward Contracts Outstanding	As of December 31, 2018 , the Company had the following net notional foreign currency forward contracts outstanding (in thousands): Foreign Currency Currency Denomination Australian dollars AUD 18,200 Brazilian Real BRL 5,500 British pounds sterling GBP 14,100 Canadian dollars CAD 2,350 Chinese renminbi CNY 41,800 Danish krone DKK 6,329 Euro EUR 9,736 Hong Kong dollars HKD 20,600 Indian rupees INR 62,000 Japanese yen JPY 2,300,000 Korean Won KRW 150,000 New Zealand Dollar NZD 100 Singapore dollars SGD 13,500 Swiss francs CHF 19,450

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Net Income Per Share Basic And Diluted	The following table sets forth the computation of basic and diluted net income per share (in thousands, except per share information): Year Ended December 31, 2018 2017 2016 Numerator: Income from continuing operations $ 575,667 $ 21,985 $ 469,855 (Loss) income from discontinued operations, net of income taxes — (42,704 ) 66,257 Net income (loss) $ 575,667 $ (20,719 ) $ 536,112 Denominator: Denominator for basic earnings per share - weighted-average shares outstanding 136,030 150,779 155,134 Effect of dilutive employee stock awards 2,653 2,493 1,950 Effect of dilutive Convertible Notes 5,769 2,231 — Effect of dilutive warrants 1,482 — — Denominator for diluted earnings per share - weighted-average shares outstanding 145,934 155,503 157,084 Basic earnings (loss) per share: Income from continuing operations $ 4.23 $ 0.15 $ 3.03 (Loss) income from discontinued operations, net of income taxes — (0.28 ) 0.43 Basic net earnings (loss) per share $ 4.23 $ (0.13 ) $ 3.46 Diluted earnings (loss) per share: Income from continuing operations $ 3.94 $ 0.14 $ 2.99 (Loss) income from discontinued operations, net of income taxes — (0.27 ) 0.42 Diluted net earnings (loss) per share: $ 3.94 $ (0.13 ) $ 3.41

Comprehensive Income (Tables)

Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Schedule of Changes in Accumulated Other Comprehensive Income by Component	The changes in Accumulated other comprehensive loss by component, net of tax, are as follows: Foreign currency Unrealized loss on available-for-sale securities Unrealized gain (loss) on derivative instruments Other comprehensive loss on pension liability Total (In thousands) Balance at December 31, 2017 $ (2,946 ) $ (6,666 ) $ 2,158 $ (3,352 ) $ (10,806 ) Other comprehensive (loss) income before reclassifications — (1,770 ) (3,842 ) 1,569 (4,043 ) Amounts reclassified from accumulated other comprehensive loss — 5,996 699 — 6,695 Net current period other comprehensive income (loss) — 4,226 (3,143 ) 1,569 2,652 Balance at December 31, 2018 $ (2,946 ) $ (2,440 ) $ (985 ) $ (1,783 ) $ (8,154 )
Schedule of Reclassification out of Accumulated Other Comprehensive Income	Reclassifications out of Accumulated other comprehensive loss are as follows: For the Year Ended December 31, 2018 (In thousands) Details about accumulated other comprehensive loss components Amount reclassified from Accumulated other comprehensive loss, net of tax Affected line item in the Consolidated Statements of Income Unrealized net loss on available-for-sale securities $ 5,996 Other income (expense), net Unrealized net loss on cash flow hedges 699 Operating expenses * $ 6,695 * Operating expenses amounts allocated to Research and development, Sales, marketing and services, and General and administrative are not individually significant.

Restructuring (Tables)

Restructuring (Tables)	12 Months Ended
	Dec. 31, 2018
Restructuring and Related Activities [Abstract]
Schedule of Restructuring Charges	For the years ended December 31, 2018 , 2017 and 2016 , restructuring charges from continuing operations were comprised of the following (in thousands): Year Ended December 31, 2018 2017 2016 Employee severance and related costs $ 2,507 $ 62,844 $ 41,054 Consolidation of leased facilities 14,218 9,718 28,857 Reversal of previous charges — (187 ) (2,510 ) Total Restructuring charges $ 16,725 $ 72,375 $ 67,401
Schedule of Restructuring Reserve	The activity in the Company’s restructuring accruals for the year ended December 31, 2018 is summarized as follows (in thousands): Total Balance at January 1, 2018 $ 55,283 Restructuring charges 16,725 Payments (26,913 ) Balance at December 31, 2018 $ 45,095

Quarterly Financial Informati_2

Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Data [Abstract]
Schedule of quarterly financial information (unaudited)	First Quarter Second Quarter Third Quarter Fourth Quarter Total Year (In thousands, except per share amounts) 2018 Net revenues $ 697,192 $ 742,365 $ 732,476 $ 801,870 $ 2,973,903 Gross margin 588,906 633,616 628,559 689,019 2,540,100 Income from operations 165,563 145,147 164,779 202,471 677,960 Net income 144,259 106,833 158,857 165,718 575,667 Earnings per share - basic 1.04 0.79 1.18 1.24 4.23 Earnings per share - diluted 0.99 0.73 1.08 1.15 3.94 First Quarter Second Quarter Third Quarter Fourth Quarter Total Year (In thousands, except per share amounts) 2017 Net revenues $ 662,677 $ 693,227 $ 690,925 $ 777,857 $ 2,824,686 Gross margin 560,219 583,915 584,988 655,918 2,385,040 Income from continuing operations 70,325 108,829 126,720 (283,889 ) 21,985 Loss from discontinued operations, net of tax (42,704 ) — — — (42,704 ) Net income 27,621 108,829 126,720 (283,889 ) (20,719 ) Basic earnings per share: Income (loss) from continuing operations 0.46 0.72 0.84 (1.93 ) 0.15 Loss from discontinued operations (0.28 ) — — — (0.28 ) Basic earnings (loss) per share 0.18 0.72 0.84 (1.93 ) (0.13 ) Diluted earnings per share: Income (loss) from continuing operations 0.44 0.70 0.82 (1.93 ) 0.14 Loss from discontinued operations (0.27 ) — — — (0.27 ) Diluted earnings (loss) per share 0.17 0.70 0.82 (1.93 ) (0.13 )

Background and Organization Bac

Background and Organization Background and Organization (Details)	12 Months Ended
	Dec. 31, 2018segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable segments	1

Significant Accounting Polici_4

Significant Accounting Policies (Impact of Adoption of ASU 2014-09) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016		Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	$ 4,169,019				$ 3,509,484				$ 4,169,019	$ 3,509,484
Deferred income tax expense									(13,156)	94,158		$ (21,654)
Total net revenues	801,870	$ 732,476	$ 742,365	$ 697,192	777,857	$ 690,925	$ 693,227	$ 662,677	2,973,903	2,824,686	[1],[2]	2,736,080	[1],[2]
Total cost of net revenues									433,803	439,646		404,889
Gross profit	689,019	628,559	633,616	588,906	655,918	584,988	583,915	560,219	2,540,100	2,385,040		2,331,191
Total operating expenses									1,862,140	1,814,043		1,771,027
Income from operations	202,471	164,779	145,147	165,563					677,960	570,997		560,164
Net income	$ 165,718	$ 158,857	$ 106,833	$ 144,259	$ (283,889)	$ 126,720	$ 108,829	$ 27,621	$ 575,667	$ (20,719)		$ 536,112
Basic earnings earnings per share (USD per share)	$ 1.24	$ 1.18	$ 0.79	$ 1.04	$ (1.93)	$ 0.84	$ 0.72	$ 0.18	$ 4.23	$ (0.13)		$ 3.46
Diluted earnings per share (USD per share)	$ 1.15	$ 1.08	$ 0.73	$ 0.99	$ (1.93)	$ 0.82	$ 0.70	$ 0.17	$ 3.94	$ (0.13)		$ 3.41
Prepaid expenses and other current assets	$ 174,195				$ 147,330				$ 174,195	$ 147,330
Other assets	124,578				52,685				124,578	52,685
Deferred tax assets, net	136,998				152,362				136,998	152,362
Total assets	5,136,049				5,820,176				5,136,049	5,820,176
Other liabilities	148,499				121,936				148,499	121,936
Current portion of deferred revenues	1,345,243				1,308,474				1,345,243	1,308,474				$ 1,250,000
Long-term portion of deferred revenues	489,329				555,769				489,329	555,769				512,800
Total liabilities	4,576,420								4,576,420
Deferred tax liabilities	49,187				$ 10,518				49,187	$ 10,518
Balances without adoption of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	4,009,637								4,009,637
Total net revenues									2,966,848
Total cost of net revenues									431,974
Gross profit									2,534,874
Total operating expenses									1,890,692
Income from operations									644,182
Net income									$ 548,430
Basic earnings earnings per share (USD per share)									$ 4.03
Diluted earnings per share (USD per share)									$ 3.76
Prepaid expenses and other current assets	147,554								$ 147,554
Other assets	52,732								52,732
Deferred tax assets, net	169,064								169,064
Total assets	5,069,628								5,069,628
Other liabilities	135,430								135,430
Current portion of deferred revenues	1,413,839								1,413,839
Long-term portion of deferred revenues	526,763								526,763
Total liabilities	4,669,381								4,669,381
Deferred tax liabilities	56,600								56,600
Accounting Standards Update 2014-09 | Effect of Change Higher/(Lower)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	159,382								159,382					130,700
Relative stand-alone selling price									99,900
Contract assets														$ 7,300
Sales commissions and fees									66,400
Deferred income tax expense		$ 42,900
Total net revenues									7,055
Total cost of net revenues									1,829
Gross profit									5,226
Total operating expenses									(28,552)
Income from operations									33,778
Net income									$ 27,237
Basic earnings earnings per share (USD per share)									$ 0.20
Diluted earnings per share (USD per share)									$ 0.18
Prepaid expenses and other current assets	26,641								$ 26,641
Other assets	71,846								71,846
Deferred tax assets, net	(32,066)								(32,066)
Total assets	66,421								66,421
Other liabilities	13,069								13,069
Current portion of deferred revenues	(68,596)								(68,596)
Long-term portion of deferred revenues	(37,434)								(37,434)
Total liabilities	(92,961)								(92,961)
Prepaid expenses and other current assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract acquisition costs	41,000								41,000
Prepaid expenses and other current assets | Balances without adoption of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract acquisition costs	14,200								14,200
Other assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract acquisition costs	68,200								68,200
Other liabilities
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred tax liabilities	$ 54,700								$ 54,700
[1]	As noted above, prior period amounts have not been adjusted under the modified retrospective method of adoption of therevenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenuerecognition standard.
[2]	Prior period amounts have not been adjusted under the modified retrospective method of adoption of the revenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenue recognition standard.

Significant Accounting Polici_5

Significant Accounting Policies (Reclassifications) (Details) - USD ($) $ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2018

Sep. 30, 2018

Jun. 30, 2018

Mar. 31, 2018

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Revenues

$ 801,870

$ 732,476

$ 742,365

$ 697,192

$ 777,857

$ 690,925

$ 693,227

$ 662,677

$ 2,973,903

$ 2,824,686

[1],[2]

$ 2,736,080

[1],[2]

As Previously Reported

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Software as a service

175,762

134,682

Revenues

2,824,686

2,736,080

Amount Reclassified

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Software as a service

138,973

110,924

Revenues

0

0

Subscription

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Revenues

455,276

314,735

245,606

Product and licenses

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Revenues

734,495

766,777

810,975

Product and licenses | As Previously Reported

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Revenues

[3]

857,253

882,898

Product and licenses | Amount Reclassified

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Revenues

[3]

(90,476)

(71,923)

Support and services

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Revenues

$ 1,784,132

1,743,174

1,679,499

Support and services | As Previously Reported

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Revenues

[4]

1,659,936

1,587,271

Support and services | Amount Reclassified

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Revenues

[4]

83,238

92,228

Professional services | As Previously Reported

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Revenues

131,735

131,229

Professional services | Amount Reclassified

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Revenues

$ (131,735)

$ (131,229)

[1]

As noted above, prior period amounts have not been adjusted under the modified retrospective method of adoption of therevenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenuerecognition standard.

[2]

Prior period amounts have not been adjusted under the modified retrospective method of adoption of the revenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenue recognition standard.

[3]

Product and licenses as previously reported included revenue from CSPs and on-premise subscriptions that are now included in Subscription. Current period presentation only includes revenues from perpetual offerings and hardware.

[4]

License updates and maintenance as previously reported included revenue from CSPs and on-premise license updates and maintenance that are now included in Subscription.

Significant Accounting Polici_6

Significant Accounting Policies (Narrative) (Details)	12 Months Ended
	Dec. 31, 2018USD ($)customerdistributor	Dec. 31, 2017USD ($)customerdistributor	Dec. 31, 2016USD ($)	Jan. 01, 2019USD ($)
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets	6 years 1 month 21 days	6 years 2 months 12 days
Amortization of capitalized contract costs	$ 38,100,000
Asset impairment charges related to contract assets	0
Allowance for doubtful accounts	3,600,000	$ 3,400,000
Amount capitalized related to internal use software	14,800,000	41,500,000
Amount expensed related to internal use software	25,900,000	27,300,000	$ 37,800,000
Capitalized costs for internally developed software to be sold as a service	7,300,000	15,200,000
Amount expensed related to internally developed computer software to be sold as a service	14,400,000	18,500,000	16,800,000
Advertising costs	99,100,000	85,600,000	72,800,000
Pension Plan | Foreign Plan
Significant Accounting Policies [Line Items]
Termination indemnities	11,200,000	13,200,000
Termination indemnities, compensation expense	$ 1,800,000	$ 2,600,000	$ 2,500,000
Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets	3 years
Licensing agreement term	1 year
Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets	7 years
Licensing agreement term	5 years
Customer concentration risk | Accounts receivable
Significant Accounting Policies [Line Items]
Number of major distributors | distributor	1	1
Number of customers meeting concentration risk threshold | customer	1	1
Contract-Based Intangible Assets [Member] | Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets	2 years
Contract-Based Intangible Assets [Member] | Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets	5 years
Internal use software | Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets	3 years
Internal use software | Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets	7 years
Internally developed software to be sold as a service
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets	2 years
Arrow Group | Customer concentration risk | Accounts receivable
Significant Accounting Policies [Line Items]
Concentration risk percentage	17.00%	14.00%
Forecast | Minimum
Significant Accounting Policies [Line Items]
Operating lease, right-of-use assets				$ 200,000,000
Operating lease, liabilities				200,000,000
Forecast | Maximum
Significant Accounting Policies [Line Items]
Operating lease, right-of-use assets				250,000,000
Operating lease, liabilities				$ 250,000,000

Significant Accounting Polici_7

Significant Accounting Policies (Property and Equipment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Retirement of property and equipment	$ 13,400	$ 16,900
Property and equipment, gross	959,767	883,231
Less: accumulated depreciation and amortization	(741,587)	(675,892)
Total property and equipment, net	$ 243,396	252,932
Buildings
Property, Plant and Equipment [Line Items]
Estimated useful lives of property and equipment	40 years
Property and equipment, gross	$ 76,152	76,152
Computer equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives of property and equipment	3 years
Property and equipment, gross	$ 189,333	176,140
Software
Property, Plant and Equipment [Line Items]
Estimated useful lives of property and equipment	3 years
Property and equipment, gross	$ 433,033	388,583
Equipment and furniture
Property, Plant and Equipment [Line Items]
Estimated useful lives of property and equipment	7 years
Property and equipment, gross	$ 78,401	73,700
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 182,848	168,656
Leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives of property and equipment	10 years
Assets under construction
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 16,769	16,769
Land
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 8,447	$ 28,824

Significant Accounting Polici_8

Significant Accounting Policies (Changes in Goodwill) (Details)	3 Months Ended		12 Months Ended
	Sep. 30, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2018USD ($)reporting_unit		Dec. 31, 2017USD ($)reporting_unit
Goodwill [Line Items]
Amortization of intangible assets					$ 18,000,000
Goodwill and intangible asset impairment	$ 0	$ 0
Number of goodwill reporting units | reporting_unit			1		2
Goodwill [Roll Forward]
Beginning balance			$ 1,614,494,000		$ 1,585,893,000
Additions			188,176,000	[1]	28,601,000	[2]
Other			0		0
Ending balance		$ 1,614,494,000	$ 1,802,670,000		1,614,494,000
Impairment of Product-related Intangible Assets
Goodwill [Line Items]
Amortization of intangible assets					15,500,000
Impairment of Other Intangible Assets
Goodwill [Line Items]
Amortization of intangible assets					$ 2,500,000
[1]	Amount relates to preliminary purchase price allocation of goodwill associated with the 2018 business combinations. See Note 4 for more information regarding the Company's acquisitions.
[2]	Amount relates to the purchase price allocation of goodwill associated with the 2017 business combination. See Note 4 for more information regarding the Company's acquisitions.

Significant Accounting Polici_9

Significant Accounting Policies (Intangible Assets) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)reporting_unit	Dec. 31, 2017USD ($)reporting_unit
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets		$ 18,000
Gross Carrying Amount	$ 974,074	885,927
Accumulated Amortization	$ 806,887	$ 743,975
Weighted-Average Life (Years)	6 years 1 month 21 days	6 years 2 months 12 days
Finite-Lived Intangible Assets, Net	$ 167,187	$ 1,600
Number of goodwill reporting units | reporting_unit	1	2
Product related intangible assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 746,152	$ 663,004
Accumulated Amortization	$ 601,993	$ 554,934
Weighted-Average Life (Years)	6 years 22 days	6 years 1 month 6 days
Other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 227,922	$ 222,923
Accumulated Amortization	$ 204,894	$ 189,041
Weighted-Average Life (Years)	6 years 4 months 24 days	6 years 5 months 27 days
Patents
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Life (Years)	10 years
Minimum
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Life (Years)	3 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Life (Years)	7 years
Cost of net revenues | Product related intangible assets
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 47,100	$ 65,700
Operating expenses | Other
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 15,900	17,200
Impairment of Product-related Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets		15,500
Impairment of Other Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets		$ 2,500

Significant Accounting Polic_10

Significant Accounting Policies (Estimated Future Annual Amortization Expense of Intangible Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
2,019	$ 50,981
2,020	38,482
2,021	24,494
2,022	22,644
2,023	19,292
Thereafter	11,294
Total	$ 167,187	$ 1,600

Significant Accounting Polic_11

Significant Accounting Policies (Revenue Recognition) (Details) - USD ($)	Jan. 01, 2018	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016	[1],[2]
Disaggregation of Revenue [Line Items]
Total net revenues		$ 801,870,000	$ 732,476,000	$ 742,365,000	$ 697,192,000	$ 777,857,000	$ 690,925,000	$ 693,227,000	$ 662,677,000	$ 2,973,903,000	$ 2,824,686,000	[1],[2]	$ 2,736,080,000
Current portion of deferred revenues	$ 1,250,000,000	1,345,243,000				1,308,474,000				1,345,243,000	1,308,474,000
Long-term portion of deferred revenues	512,800,000	$ 489,329,000				$ 555,769,000				489,329,000	$ 555,769,000
Deferred revenue recognized	$ 1,250,000,000
Asset impairment charges related to contract assets										0
Products and services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total net revenues										821,111,000
Products and services transferred over time
Disaggregation of Revenue [Line Items]
Total net revenues										$ 2,152,792,000
[1]	As noted above, prior period amounts have not been adjusted under the modified retrospective method of adoption of therevenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenuerecognition standard.
[2]	Prior period amounts have not been adjusted under the modified retrospective method of adoption of the revenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenue recognition standard.

Significant Accounting Polic_12

Significant Accounting Policies (Remaining Performance Obligations) (Details) $ in Thousands	Dec. 31, 2018USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	2 years
Total net revenues	$ 2,068,914
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01 | Subscription
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	2 years
Total net revenues	$ 431,527
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01 | Support and services
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	2 years
Total net revenues	$ 1,637,387
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	2 years
Total net revenues	$ 101,528
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01 | Subscription
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	2 years
Total net revenues	$ 45,790
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01 | Support and services
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	2 years
Total net revenues	$ 55,738
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period
Total net revenues	$ 2,594
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01 | Subscription
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period
Total net revenues	$ 535
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01 | Support and services
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period
Total net revenues	$ 2,059
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total net revenues	2,173,036
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil) | Subscription
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total net revenues	477,852
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil) | Support and services
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total net revenues	$ 1,695,184

Discontinued Operations - Finan

Discontinued Operations - Financial Statement Information (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense					$ 0	$ 2,900	$ 22,737
(Loss) income from discontinued operations, net of income tax	$ 0	$ 0	$ 0	$ (42,704)	0	(42,704)	66,257
Separation costs						500	2,500
Cumulative-effect adjustment from adoption of accounting standards					132,778	388
Spinoff transaction						461,831
Transfer of cash					0	28,523	0
GoTo Business Division
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net revenues						58,215	682,185
Cost of net revenues						15,456	154,652
Gross margin						42,759	527,533
Research and development						9,108	93,892
Sales, marketing and services						20,881	209,475
General and administrative						7,636	63,270
Amortization of other intangible assets						1,176	14,097
Restructuring						3,189	3,721
Separation						40,573	54,084
Total operating expenses						82,563	438,539
(Loss) income from discontinued operations before income taxes						(39,804)	88,994
Income tax expense						2,900	22,737
(Loss) income from discontinued operations, net of income tax						(42,704)	$ 66,257
Retained Earnings
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cumulative-effect adjustment from adoption of accounting standards					$ 132,778	(5,303)
Spinoff transaction						475,231
Foreign currency | GoTo Business Division
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Distribution of the GoTo Business						$ 13,400

Acquisitions (Narrative) (Detai

Acquisitions (Narrative) (Details) - USD ($) $ in Millions	Nov. 13, 2018	Feb. 06, 2018	Jan. 03, 2017
Sapho, Inc.
Business Acquisition [Line Items]
Total consideration in business acquisitions	$ 182.9
Cash acquired from the acquisition	$ 3.7
Cedexis, Inc.
Business Acquisition [Line Items]
Total consideration in business acquisitions		$ 66
Cash acquired from the acquisition		$ 6
Unidesk
Business Acquisition [Line Items]
Total consideration in business acquisitions			$ 60.4
Cash acquired from the acquisition			$ 2.7

Acquisitions - Schedule of Asse

Acquisitions - Schedule of Assets and Liabilities Acquired (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill	$ 1,802,670	$ 1,614,494	$ 1,585,893
Sapho, Inc.
Business Acquisition [Line Items]
Current assets	4,671
Intangible assets	53,600
Goodwill	144,173
Deferred taxes	0
Other assets	0
Assets acquired	202,444
Other current liabilities assumed	3,323
Assumed debt	0
Other long term liabilities assumed	370
Deferred taxes	12,094
Net assets acquired	$ 186,657
Weighted average useful life	5 years
Cedexis, Inc.
Business Acquisition [Line Items]
Current assets	$ 8,961
Intangible assets	27,200
Goodwill	44,003
Deferred taxes	3,173
Other assets	69
Assets acquired	83,406
Other current liabilities assumed	5,711
Assumed debt	5,674
Other long term liabilities assumed	0
Deferred taxes	0
Net assets acquired	$ 72,021
Minimum | Cedexis, Inc.
Business Acquisition [Line Items]
Weighted average useful life	1 year
Maximum | Cedexis, Inc.
Business Acquisition [Line Items]
Weighted average useful life	6 years

Acquisitions - Intangible Asset

Acquisitions - Intangible Assets Acquired (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Sapho, Inc.
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets acquired	$ 53,600
Weighted average useful life	5 years
Sapho, Inc. | Customer Contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets acquired	$ 1,600
Weighted average useful life	5 years
Sapho, Inc. | Developed Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets acquired	$ 52,000
Weighted average useful life	5 years
Sapho, Inc. | Tradenames
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets acquired	$ 0
Cedexis, Inc.
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets acquired	27,200
Cedexis, Inc. | Customer Contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets acquired	$ 2,000
Weighted average useful life	1 year
Cedexis, Inc. | Developed Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets acquired	$ 23,800
Cedexis, Inc. | Tradenames
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets acquired	$ 1,400
Weighted average useful life	1 year
Minimum | Cedexis, Inc.
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life	1 year
Minimum | Cedexis, Inc. | Developed Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life	5 years
Maximum | Cedexis, Inc.
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life	6 years
Maximum | Cedexis, Inc. | Developed Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life	6 years

Acquisitions - Pro-forma Inform

Acquisitions - Pro-forma Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Business Combinations [Abstract]
Revenues	$ 2,977,155	$ 2,838,880
Income from continuing operations	651,047	530,470
Net income (loss)	$ 550,985	$ (56,601)

Investments (Narrative) (Detail

Investments (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Investment [Line Items]
Average remaining maturities for short-term available for sale investments, in months	6 months
Average remaining maturities for long-term available for sale investments, in years	2 years
Realized gains on the sales of available-for-sale investments	$ 100,000	$ 800,000
Realized losses on the sales of available-for-sale investments	1,500,000	500,000
Other-than-temporary impairment, available-for-sale securities	4,600,000
Gross realized losses on available-for-sale securities not deemed other-than-temporary	2,900,000	7,300,000
Significant Unobservable Inputs (Level 3)
Investment [Line Items]
Adjustments to direct investments in privately-held companies	0
Private Equity Funds
Investment [Line Items]
Alternative Investment	10,900,000
Other Assets
Investment [Line Items]
Direct investments in privately-held companies	$ 13,400,000
Cost method investments		$ 18,600,000

Investments (Schedule Of Availa

Investments (Schedule Of Available-For-Sale Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,164,848	$ 1,623,319
Gross Unrealized Gains	544	823
Gross Unrealized Losses	(7,458)	(7,298)
Fair Value	1,157,934	1,616,844
Agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	314,982	441,315
Gross Unrealized Gains	333	509
Gross Unrealized Losses	(2,367)	(2,760)
Fair Value	312,948	439,064
Corporate securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	612,698	810,444
Gross Unrealized Gains	116	268
Gross Unrealized Losses	(4,156)	(3,020)
Fair Value	608,658	807,692
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,500	3,965
Gross Unrealized Gains	4	2
Gross Unrealized Losses	0	(2)
Fair Value	2,504	3,965
Government securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	234,668	367,595
Gross Unrealized Gains	91	44
Gross Unrealized Losses	(935)	(1,516)
Fair Value	$ 233,824	$ 366,123

Fair Value Measurements (Assets

Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - Recurring basis - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Quoted Prices In Active Markets for Identical Assets (Level 1)
Assets, Fair Value Disclosure [Abstract]
Total assets	$ 593,489	$ 1,112,346
Liabilities, Fair Value Disclosure [Abstract]
Total liabilities	0	0
Significant Other Observable Inputs (Level 2)
Assets, Fair Value Disclosure [Abstract]
Total assets	1,183,262	1,621,733
Liabilities, Fair Value Disclosure [Abstract]
Total liabilities	2,543	814
Significant Unobservable Inputs (Level 3)
Assets, Fair Value Disclosure [Abstract]
Total assets	713	393
Liabilities, Fair Value Disclosure [Abstract]
Total liabilities	0	0
Cash and cash equivalents | Cash | Quoted Prices In Active Markets for Identical Assets (Level 1)
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	505,363	556,520
Cash and cash equivalents | Cash | Significant Other Observable Inputs (Level 2)
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0	0
Cash and cash equivalents | Cash | Significant Unobservable Inputs (Level 3)
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0	0
Cash and cash equivalents | Money market funds | Quoted Prices In Active Markets for Identical Assets (Level 1)
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	88,126	555,826
Cash and cash equivalents | Money market funds | Significant Other Observable Inputs (Level 2)
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0	0
Cash and cash equivalents | Money market funds | Significant Unobservable Inputs (Level 3)
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0	0
Cash and cash equivalents | Corporate securities | Quoted Prices In Active Markets for Identical Assets (Level 1)
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0	0
Cash and cash equivalents | Corporate securities | Significant Other Observable Inputs (Level 2)
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	9,371	2,784
Cash and cash equivalents | Corporate securities | Significant Unobservable Inputs (Level 3)
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0	0
Cash and cash equivalents | Government securities | Quoted Prices In Active Markets for Identical Assets (Level 1)
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents
Cash and cash equivalents | Government securities | Significant Other Observable Inputs (Level 2)
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	12,610
Cash and cash equivalents | Government securities | Significant Unobservable Inputs (Level 3)
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0
Agency securities | Money market funds | Quoted Prices In Active Markets for Identical Assets (Level 1)
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0
Agency securities | Money market funds | Significant Other Observable Inputs (Level 2)
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	3,296
Agency securities | Money market funds | Significant Unobservable Inputs (Level 3)
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0
Available-for-sale securities | Agency securities | Quoted Prices In Active Markets for Identical Assets (Level 1)
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	0	0
Available-for-sale securities | Agency securities | Significant Other Observable Inputs (Level 2)
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	312,948	439,064
Available-for-sale securities | Agency securities | Significant Unobservable Inputs (Level 3)
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	0	0
Available-for-sale securities | Corporate securities | Quoted Prices In Active Markets for Identical Assets (Level 1)
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	0	0
Available-for-sale securities | Corporate securities | Significant Other Observable Inputs (Level 2)
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	607,945	807,299
Available-for-sale securities | Corporate securities | Significant Unobservable Inputs (Level 3)
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	713	393
Available-for-sale securities | Municipal securities | Quoted Prices In Active Markets for Identical Assets (Level 1)
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	0	0
Available-for-sale securities | Municipal securities | Significant Other Observable Inputs (Level 2)
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	2,504	3,965
Available-for-sale securities | Municipal securities | Significant Unobservable Inputs (Level 3)
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	0	0
Available-for-sale securities | Government securities | Quoted Prices In Active Markets for Identical Assets (Level 1)
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	0	0
Available-for-sale securities | Government securities | Significant Other Observable Inputs (Level 2)
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	233,824	366,123
Available-for-sale securities | Government securities | Significant Unobservable Inputs (Level 3)
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	0	0
Accrued expenses and other current liabilities | Quoted Prices In Active Markets for Identical Assets (Level 1)
Liabilities, Fair Value Disclosure [Abstract]
Foreign currency derivatives	0	0
Accrued expenses and other current liabilities | Significant Other Observable Inputs (Level 2)
Liabilities, Fair Value Disclosure [Abstract]
Foreign currency derivatives	2,543	814
Accrued expenses and other current liabilities | Significant Unobservable Inputs (Level 3)
Liabilities, Fair Value Disclosure [Abstract]
Foreign currency derivatives	0	0
Estimate of Fair Value Measurement
Assets, Fair Value Disclosure [Abstract]
Total assets	1,777,464	2,734,472
Liabilities, Fair Value Disclosure [Abstract]
Total liabilities	2,543	814
Estimate of Fair Value Measurement | Cash and cash equivalents | Cash
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	505,363	556,520
Estimate of Fair Value Measurement | Cash and cash equivalents | Money market funds
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	88,126	555,826
Estimate of Fair Value Measurement | Cash and cash equivalents | Corporate securities
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	9,371	2,784
Estimate of Fair Value Measurement | Cash and cash equivalents | Government securities
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	12,610
Estimate of Fair Value Measurement | Agency securities | Money market funds
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	3,296
Estimate of Fair Value Measurement | Available-for-sale securities | Agency securities
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	312,948	439,064
Estimate of Fair Value Measurement | Available-for-sale securities | Corporate securities
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	608,658	807,692
Estimate of Fair Value Measurement | Available-for-sale securities | Municipal securities
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	2,504	3,965
Estimate of Fair Value Measurement | Available-for-sale securities | Government securities
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	233,824	366,123
Estimate of Fair Value Measurement | Accrued expenses and other current liabilities
Liabilities, Fair Value Disclosure [Abstract]
Foreign currency derivatives	2,543	814
Foreign currency | Prepaid expenses and other current assets | Quoted Prices In Active Markets for Identical Assets (Level 1)
Assets, Fair Value Disclosure [Abstract]
Derivative assets fair value	0	0
Foreign currency | Prepaid expenses and other current assets | Significant Other Observable Inputs (Level 2)
Assets, Fair Value Disclosure [Abstract]
Derivative assets fair value	764	2,498
Foreign currency | Prepaid expenses and other current assets | Significant Unobservable Inputs (Level 3)
Assets, Fair Value Disclosure [Abstract]
Derivative assets fair value	0	0
Foreign currency | Estimate of Fair Value Measurement | Prepaid expenses and other current assets
Assets, Fair Value Disclosure [Abstract]
Derivative assets fair value	$ 764	$ 2,498

Fair Value Measurements (Asse_2

Fair Value Measurements (Assets Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cost method investments, fair value		$ 1,200,000
Impairment of cost-method investments		1,400,000
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Adjustments to direct investments in privately-held companies	$ 0
Fair Value, Measurements, Nonrecurring [Member] | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities without Readily Determinable Fair Value, Amount	2,800,000
Equity Securities, FV-NI and without Readily Determinable Fair Value	1,900,000
Other (expense) income, net | Fair Value, Measurements, Nonrecurring [Member] | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Adjustments to direct investments in privately-held companies	$ 900,000
Impaired Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cost method investments		$ 2,600,000

Fair Value Measurements (Additi

Fair Value Measurements (Additional Disclosures Regarding Fair Value Measurements) (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Apr. 30, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, Carrying Value	$ 741,825,000	$ 2,127,474,000
Level 2 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Closing trading price per $100 as of the last day of trading for the year	100
Convertible Senior Notes, Fair Value	1,648,567,000
Convertible Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible Senior Notes, Carrying Value	1,155,445,000	$ 1,386,324,000	$ 1,440,000,000
Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, Carrying Value	741,825,000
Senior Notes | Level 2 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, Fair Value	$ 717,375,000

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities (Schedule of Accrued Expenses and Other Current Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts Payable and Accrued Liabilities, Current [Abstract]
Accrued compensation and employee benefits	$ 196,847	$ 161,049
Other accrued expenses	93,645	116,630
Total	$ 290,492	$ 277,679

Employee Stock-Based Compensa_3

Employee Stock-Based Compensation and Benefit Plans (Narrative) (Details) $ / shares in Units, $ in Thousands	Aug. 01, 2017shares	Mar. 31, 2018shares	Mar. 31, 2017$ / sharesshares	Mar. 31, 2016$ / sharesshares	Jan. 31, 2016$ / sharesshares	Mar. 31, 2018	Dec. 31, 2018USD ($)installmentplan$ / sharesshares	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock-based compensation plans offered | plan							1
Stock-based compensation | $							$ 203,619	$ 165,120	$ 152,739
Deferred tax asset related to stock-based compensation | $							39,700	46,100	53,500
Tax benefit from compensation expense | $							$ 49,700	72,900	64,700
401(k) Benefit Plan [Abstract]
Maximum annual contribution per employee (as a percent)							90.00%
Contribution per dollar of employee contribution							50.00%
Matching percent							3.00%
Defined Contribution Plan, Cost | $							$ 13,000	13,700	14,000
Market and service condition stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested stock unit awards granted to senior level employees (shares)			275,148	234,816
Performance period			3 years
Total return to shareholders as percentile of peer group, minimum			41.00%
Total return to shareholders as percentile of peer group, maximum			80.00%
Maximum share cap based on target shareholder return (percent)			100.00%
Minimum share cap based on target shareholder return (percent)			200.00%
Minimum peer group percentile to achieve target share cap			80.00%
Period to determine actual stock grant following end of interim measurement period			60 days
Non-vested stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation | $							$ 193,800	149,800	135,700
Non-vested stock unit awards granted to senior level employees (shares)							3,903,225
Expected volatility rate, calculation basis, period			2 years 9 months			3 years
Granted (in dollars per share) | $ / shares			$ 104.05	$ 66.18	$ 49.68		$ 92.20
Share-based compensation award, stock vesting period, monthly installments | installment							12
Fair value of awards released | $							$ 149,300	$ 150,000	163,800
Total unrecognized compensation cost related to stock-based compensation | $							$ 376,700
Total unrecognized compensation cost recognition period (in years)							1 year 9 months 5 days
Non-vested stock | Annual vesting on each anniversary
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage							33.33%
Non-vested stock (Modified)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility rate, calculation basis, period			1 year 22 days
Granted (in dollars per share) | $ / shares			$ 99.54
Performance stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period				3 years
Maximum target shareholder return (percent)				10.00%
Maximum share cap based on target shareholder return (percent)				100.00%
Minimum target shareholder return (percent)				5.00%
Minimum share cap based on target shareholder return (percent)				200.00%
Target shareholder return maximum to attain 200% (percent)				30.00%
Period to determine actual stock grant following end of interim measurement period				60 days
Interim measurement period				18 months
Share cap based on interim measurement period (percent)				33.00%
Period to determine actual stock grant following end of performance period	60 days	60 days		60 days
Maximum percentage of market and service condition stock units that will ultimately vest	200.00%	200.00%
Superseded Stock Plans | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period							5 years
Superseded Stock Plans | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period							10 years
2014 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance under the Plan (shares)							46,000,000
Shares reserved for issuance under the Plans (shares)							20,837,415
Shares available for grant under the 2014 Equity Incentive Plan (shares)							14,935,686
2015 ESPP Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance under the Plan (shares)							16,000,000
Employee Stock Purchase Plan, payment period							6 months
Employee Stock Purchase Plan, maximum number of shares per period that employees can purchase (shares)							12,000
Employee Stock Purchase Plan, lower of purchase price offered on either first or last day of payment period as a percentage of fair market value (percent)							85.00%
Employee Stock Purchase Plan, employee disqualification, ownership percent of outstanding stock							5.00%
Employee Stock Purchase Plan, total shares issued under plan (shares)							1,721,924
Stock-based compensation | $									$ 7,500
Expected volatility rate, calculation basis, period							6 months	6 months	6 months
2015 ESPP Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Stock Purchase Plan, option to purchase shares through payroll deduction, payroll deduction amount per pay period per employee, as a percentage of base pay							1.00%
2015 ESPP Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Stock Purchase Plan, option to purchase shares through payroll deduction, payroll deduction amount per pay period per employee, as a percentage of base pay							10.00%
Employee Stock Purchase Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation | $							$ 9,800	$ 10,000
Chief Executive Officer | Performance stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested stock unit awards granted to senior level employees (shares)					220,235
Senior Level Employees | Performance stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested stock unit awards granted to senior level employees (shares)	184,322	268,729

Employee Stock-Based Compensa_4

Employee Stock-Based Compensation and Benefit Plans (Assumptions Used To Value Option Grants) (Details)	1 Months Ended			3 Months Ended	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Jan. 31, 2016	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Non-vested stock (Modified)
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Approximate risk free interest rate	2.67%
Expected dividend yield	0.00%
Expected term (in years)	1 year 22 days
Non-vested stock (Modified) | Minimum
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected volatility factor	16.00%
Non-vested stock (Modified) | Maximum
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected volatility factor	32.00%
Non-vested stock
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Approximate risk free interest rate	1.48%	0.91%	1.10%
Expected dividend yield	0.00%	0.00%	0.00%
Expected term (in years)	2 years 9 months			3 years
Non-vested stock | Minimum
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected volatility factor	27.00%	29.00%	29.00%
Non-vested stock | Maximum
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected volatility factor	32.00%	39.00%	37.00%
ESPP Plan
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected dividend yield						0.00%	0.00%
Expected term (in years)					6 months	6 months	6 months
ESPP Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected volatility factor					26.00%	27.00%	27.00%
Approximate risk free interest rate					1.12%	0.60%	0.25%
Expected dividend yield					0.00%
ESPP Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected volatility factor					29.00%	29.00%	41.00%
Approximate risk free interest rate					2.19%	1.12%	0.42%
Expected dividend yield					1.27%

Employee Stock-Based Compensa_5

Employee Stock-Based Compensation and Benefit Plans (Detail of the Total Stock-Based Compensation Recognized by Income Statement Classification) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation	$ 203,619	$ 165,120	$ 152,739
Cost of subscription, support and services
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation	7,979	4,281	2,179
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation	66,154	47,291	38,578
Sales, marketing and services
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation	72,406	55,173	48,514
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation	$ 57,080	$ 58,375	$ 63,468

Employee Stock-Based Compensa_6

Employee Stock-Based Compensation and Benefit Plans (Schedule of Non-vested Stock Unit Activity) (Details) - Non-vested stock - $ / shares	1 Months Ended			12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Jan. 31, 2016	Dec. 31, 2018
Number of Shares
Non-vested stock units at December 31, 2017 (in shares)				4,622,546
Granted (in shares)				3,903,225
Vested (in shares)				(2,076,052)
Forfeited (in shares)				(596,218)
Non-vested stock units at December 31, 2018 (in shares)				5,853,501
Weighted- Average Fair Value at Grant Date
Non-vested stock units at December 31, 2017 (in dollars per share)				$ 82.83
Granted (in dollars per share)	$ 104.05	$ 66.18	$ 49.68	92.20
Vested (in dollars per share)				71.92
Forfeited (in dollars per share)				74.07
Non-vested stock units at December 31, 2018 (in dollars per share)				$ 88.79

Capital Stock (Narrative) (Deta

Capital Stock (Narrative) (Details) - USD ($)	Mar. 22, 2019	Dec. 21, 2018	Apr. 30, 2018	Feb. 28, 2018	Jan. 31, 2018	Nov. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2018	Jun. 30, 2014
Class of Stock [Line Items]
Stock repurchase program, authorized amount						$ 1,700,000,000				$ 750,000,000	$ 1,500,000,000
Accelerated stock repurchase program						$ 750,000,000	$ (750,000,000)	$ (750,000,000)
Available to repurchase common stock							767,900,000
Amount expended on share repurchases in open market transactions							$ 511,153,000	$ 574,956,000	$ 28,689,000
Total tax withholdings for share-based compensation (in shares)							739,522	974,501	830,155
Total tax withholdings for share-based compensation							$ 71,593,000	$ 80,040,000	$ 66,638,000
Preferred stock, shares authorized							5,000,000	5,000,000
Preferred stock, par value (in dollars per share)							$ 0.01	$ 0.01
Preferred stock, shares issued							0	0
Preferred stock, shares outstanding							0	0
Cash dividend paid (in dollars per share)		$ 0.35
Open Market Purchases
Class of Stock [Line Items]
Amount expended on share repurchases in open market transactions							$ 511,200,000	$ 575,000,000	$ 28,700,000
Number of shares repurchased							4,730,542	7,384,368	426,300
Average per share price on share repurchases in open market transactions (in dollars per share)							$ 108.05	$ 77.86	$ 67.30
ASR Counterparty
Class of Stock [Line Items]
Amount expended on share repurchases in open market transactions				$ 750,000,000			$ 750,000,000
Number of shares repurchased			1,600,000	6,500,000	1,371,495		7,100,000
Shares repurchased as percentage of shares pursuant to accelerated share repurchase agreement (percent)							80.00%
Forecast
Class of Stock [Line Items]
Cash dividend paid (in dollars per share)	$ 0.35

Commitments and Contingencies_2

Commitments and Contingencies (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)$ / square_foot	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Loss Contingencies [Line Items]
Rental expense	$ 73,800	$ 64,300	$ 84,600
Consolidation of leased facilities	14,218	9,718	28,857
Sublease income	200	$ 200	$ 200
Liability for loss on lease obligation	43,400
Purchase obligations anticipated for 2018	5,300
Contingent obligations to purchase inventory	16,600
Other purchase commitments, due in fiscal 2019	25,000
Other purchase commitments, due in fiscal 2020	25,000
One Office Location
Loss Contingencies [Line Items]
Liability for loss on lease obligation	$ 42,300
Operating lease, change in price per square foot (dollars per square foot) | $ / square_foot	0.50
Operating lease, change in price per square foot, percent	20.00%
Impact on liabilities for loss on lease obligation if price per square foot assumtion changed by $0.50	$ 4,900

Commitments and Contingencies_3

Commitments and Contingencies (Schedule of Lease Commitments) (Details) $ in Thousands	Dec. 31, 2018USD ($)
Operating Leases
2,019	$ 57,122
2,020	49,358
2,021	39,981
2,022	35,296
2,023	32,018
Thereafter	87,621
Total	301,396
Sublease Income
2,019	241
2,020	0
2,021	0
2,022	0
2,023	0
Thereafter	0
Total	$ 241

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Tax benefit attributable to the remeasurement of tax assets and liabilties	$ 26,300
2017 transition tax benefit	21,900
Federal corporate tax rate reduction	4,400
Valuation allowance	(85,400)	$ (76,789)
Federal and state GILTI tax expense	12,800
Federal and state FDII tax benefit	5,400
Provisional income tax charge for transition tax on repatriation of deferred foreign income		364,600
Provisional income tax charge for re-measurement of deferred tax assets and liabilities		64,800
Income tax charge to establish valuation allowance related to R&D credits		48,600
Tax benefit due to recognition of income tax effects related to stock based compensation		22,000
Tax benefit from release of uncertain tax positions due to expiration of statute of limitations	8,436	8,764
Unrecognized tax benefits	89,906	$ 77,849	$ 69,801
Accrued interest and penalties	3,900
Research
Operating Loss Carryforwards [Line Items]
Tax credit carryforward	116,600
United States
Operating Loss Carryforwards [Line Items]
Net operating loss carry forwards	172,300
Foreign jurisdictions
Operating Loss Carryforwards [Line Items]
Net operating loss carry forwards	111,300
Long-term Deferred Tax Assets
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits	$ 35,400

Income Taxes (United States and

Income Taxes (United States and Foreign Components of Income Before Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Expense (Benefit), Continuing Operations, by Jurisdiction [Abstract]
United States	$ 174,519	$ 78,897	$ 59,344
Foreign	454,936	471,449	468,426
Income from continuing operations before income taxes	$ 629,455	$ 550,346	$ 527,770

Income Taxes (Components of the

Income Taxes (Components of the Provision for Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal	$ (19,461)	$ 374,602	$ 18,832
Foreign	70,146	56,526	52,978
State	16,259	3,075	7,759
Total current	66,944	434,203	79,569
Deferred:
Federal	1,899	52,842	(7,688)
Foreign	(14,804)	(5,468)	(3,139)
State	(251)	46,784	(10,827)
Total deferred	(13,156)	94,158	(21,654)
Total provision	$ 53,788	$ 528,361	$ 57,915

Income Taxes (Deferred Tax Asse

Income Taxes (Deferred Tax Assets and Liabilities by Balance Sheet Classification (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets and Liabilities by Balance Sheet Classification [Abstract]
Deferred tax assets	$ 136,998	$ 152,362
Deferred tax liabilities	(15,075)	(237)
Total net deferred tax assets	$ 121,923	$ 152,125

Income Taxes (Components of Def

Income Taxes (Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Accruals and reserves	$ 27,022	$ 30,317
Deferred revenue	62,085	65,016
Tax credits	81,720	80,772
Net operating losses	54,747	36,674
Stock based compensation	30,936	21,714
Depreciation and amortization	0	4,939
Valuation allowance	(85,400)	(76,789)
Total deferred tax assets	171,110	162,643
Deferred tax liabilities:
Acquired technology	(15,681)	(2,882)
Depreciation and amortization	(5,044)	0
Prepaid expenses	(23,213)	(7,414)
Other	(5,249)	(222)
Total deferred tax liabilities	(49,187)	(10,518)
Total net deferred tax assets	$ 121,923	$ 152,125

Income Taxes (Reconciliation of

Income Taxes (Reconciliation of the Company's Effective Tax Rate to the Statutory Federal Rate) (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Federal statutory taxes	21.00%	35.00%	35.00%
State income taxes, net of federal tax benefit	0.70%	2.10%	0.80%
Foreign operations	(5.40%)	(20.00%)	(21.60%)
Permanent differences	2.00%	2.60%	3.20%
The 2017 Tax Act - tax rate impact on deferred taxes	(0.70%)	11.80%	0.00%
The 2017 Tax Act - transition tax	(3.50%)	66.30%	0.00%
Change in valuation allowance reserve	0.40%	8.80%	0.00%
Change in deferred tax liability related to acquired intangibles	(0.10%)	0.30%	(0.80%)
Tax credits	(5.80%)	(7.60%)	(7.90%)
Stock-based compensation	(1.90%)	(3.60%)	0.30%
Change in accruals for uncertain tax positions	1.80%	0.30%	2.20%
Other	0.00%	0.00%	(0.20%)
Effective income tax rate	8.50%	96.00%	11.00%

Income Taxes (Reconciliation _2

Income Taxes (Reconciliation of the Beginning and Ending Amount of Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of the Beginning and Ending Amount of Unrecognized Tax Benefits [Roll Forward]
Beginning balance	$ 77,849	$ 69,801
Additions based on tax positions related to the current year	10,168	9,293
Additions for tax positions of prior years	10,325	7,656
Reductions related to audit settlements		(137)
Reductions related to the expiration of statutes of limitations	(8,436)	(8,764)
Ending balance	$ 89,906	$ 77,849

Segment Information (Narrative)

Segment Information (Narrative) (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018USD ($)distributor	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)distributor	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2018USD ($)segmentdistributor	Dec. 31, 2017USD ($)distributor		Dec. 31, 2016USD ($)distributor
Concentration Risk [Line Items]
Number of reportable segments | segment									1
Percentage of international revenues accounting for the Company's net revenues									47.00%	46.30%		46.30%
Net revenues	$ 801,870	$ 732,476	$ 742,365	$ 697,192	$ 777,857	$ 690,925	$ 693,227	$ 662,677	$ 2,973,903	$ 2,824,686	[1],[2]	$ 2,736,080	[1],[2]
US to International Revenues
Concentration Risk [Line Items]
Net revenues									$ 141,900	$ 151,900		$ 160,500
Net revenues | Customer concentration risk
Concentration Risk [Line Items]
Number of distributors meeting concentration risk threshold | distributor	1				2				1	2		2
Ingram Micro | Net revenues | Customer concentration risk
Concentration Risk [Line Items]
Concentration risk percentage										13.00%		13.00%
Arrow Group | Net revenues | Customer concentration risk
Concentration Risk [Line Items]
Concentration risk percentage									14.00%	12.00%		12.00%
[1]	As noted above, prior period amounts have not been adjusted under the modified retrospective method of adoption of therevenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenuerecognition standard.
[2]	Prior period amounts have not been adjusted under the modified retrospective method of adoption of the revenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenue recognition standard.

Segment Information (Identifiab

Segment Information (Identifiable Assets By Segment) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Long-lived assets	$ 243,396	$ 252,932
United States
Segment Reporting Information [Line Items]
Long-lived assets	185,091	189,465
United Kingdom
Segment Reporting Information [Line Items]
Long-lived assets	25,459	24,171
Other countries
Segment Reporting Information [Line Items]
Long-lived assets	$ 32,846	$ 39,296

Segment Information (Revenues B

Segment Information (Revenues By Product Grouping) (Details) - USD ($) $ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2018

Sep. 30, 2018

Jun. 30, 2018

Mar. 31, 2018

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Segment Reporting Information [Line Items]

Net revenues

$ 801,870

$ 732,476

$ 742,365

$ 697,192

$ 777,857

$ 690,925

$ 693,227

$ 662,677

$ 2,973,903

$ 2,824,686

[1],[2]

$ 2,736,080

[1],[2]

Digital workspace

Segment Reporting Information [Line Items]

Net revenues

[3]

2,024,289

1,901,952

[2]

1,821,739

[2]

Networking

Segment Reporting Information [Line Items]

Net revenues

[4]

817,193

790,434

[2]

782,875

[2]

Professional services

Segment Reporting Information [Line Items]

Net revenues

[5]

$ 132,421

$ 132,300

[2]

$ 131,466

[2]

Net revenues | Arrow Group | Customer concentration risk

Segment Reporting Information [Line Items]

Concentration risk percentage

14.00%

12.00%

12.00%

[1]

As noted above, prior period amounts have not been adjusted under the modified retrospective method of adoption of therevenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenuerecognition standard.

[2]

Prior period amounts have not been adjusted under the modified retrospective method of adoption of the revenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenue recognition standard.

[3]

Digital Workspace revenues are primarily comprised of sales from the Company’s application virtualization solutions, which include Citrix Virtual Apps and Desktops, the Company's unified endpoint management solutions, which include Citrix Endpoint Management, related license updates and maintenance and support, Citrix Content Collaboration, and cloud offerings

[4]

Networking revenues primarily include Citrix ADC and Citrix SD-WAN, related license updates and maintenance and support and cloud offerings.

[5]

Professional services revenues are primarily comprised of revenues from consulting services and product training and certification services.

Segment Information (Revenues_2

Segment Information (Revenues By Geographic Location) (Details) - USD ($) $ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2018

Sep. 30, 2018

Jun. 30, 2018

Mar. 31, 2018

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2018

Dec. 31, 2017

[1]

Dec. 31, 2016

[1]

Revenues from External Customers and Long-Lived Assets [Line Items]

Net revenues

$ 801,870

$ 732,476

$ 742,365

$ 697,192

$ 777,857

$ 690,925

$ 693,227

$ 662,677

$ 2,973,903

$ 2,824,686

[2]

$ 2,736,080

[2]

Americas

Revenues from External Customers and Long-Lived Assets [Line Items]

Net revenues

1,716,876

1,644,008

1,598,896

EMEA

Revenues from External Customers and Long-Lived Assets [Line Items]

Net revenues

956,365

888,072

863,517

APJ

Revenues from External Customers and Long-Lived Assets [Line Items]

Net revenues

$ 300,662

$ 292,606

$ 273,667

[1]

As noted above, prior period amounts have not been adjusted under the modified retrospective method of adoption of therevenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenuerecognition standard.

[2]

Prior period amounts have not been adjusted under the modified retrospective method of adoption of the revenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenue recognition standard.

Debt (Details)

Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Apr. 30, 2014
Debt Instrument [Line Items]
Temporary equity	$ 8,110	$ 0
Additional paid-in capital	5,404,500	4,883,670
Senior Notes Due 2019
Debt Instrument [Line Items]
Principal	1,164,497	1,437,483
Less: note discount and issuance costs	(9,052)	(51,159)
Net carrying amount	1,155,445	1,386,324	$ 1,440,000
Temporary equity	8,110	0
Additional paid-in capital	127,374	162,869
Total (including temporary equity)	$ 135,484	$ 162,869

Debt - Schedule of Interest Exp

Debt - Schedule of Interest Expense (Details) - Convertible Notes and 2027 Notes - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Contractual interest expense	$ 40,151	$ 11,406	$ 7,187
Amortization of debt issuance costs	4,663	4,050	3,863
Amortization of debt discount	34,228	34,039	33,014
Interest expense	$ 79,042	$ 49,495	$ 44,064

Debt - Additional Information (

Debt - Additional Information (Details) $ / shares in Units, shares in Thousands	Nov. 15, 2017USD ($)	Apr. 30, 2014USD ($)shares	Sep. 30, 2018USD ($)day$ / shares	Dec. 31, 2018USD ($)$ / sharesshares	Jun. 30, 2014USD ($)	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Oct. 31, 2018USD ($)	Nov. 30, 2017USD ($)	Dec. 31, 2014
Debt Instrument [Line Items]
Proceeds from 2027 notes, net of issuance costs						$ 0	$ 741,039,000	$ 0
Stock repurchase program, authorized amount					$ 1,500,000,000				$ 750,000,000	$ 1,700,000,000
Payments for repurchase of common stock						1,261,153,000	1,174,957,000	$ 28,689,000
Convertible notes, short-term				$ 1,155,445,000		1,155,445,000	0
Temporary equity				8,110,000		8,110,000	0
Convertible Debt, Conversion Notices Received, Amount			$ 273,000,000
Senior Notes Due 2019
Debt Instrument [Line Items]
Principal amount of notes				1,000		1,000
Stated interest rate (percent)											0.50%
Convertible debt		$ 1,440,000,000		$ 1,155,445,000		$ 1,155,445,000	1,386,324,000
Proceeds from convertible debt offering		1,420,000,000
Net proceeds used to pay the cost of Bind Hedges		$ 82,600,000
Convertible debt, conversion ratio						0.0139510
Convertible debt, conversion price (in dollars per share) | $ / shares				$ 71.68		$ 71.68
Repurchase price as a percent of principal amount (percent)		100.00%
Effective interest rate (percent)						3.00%
Convertible Debt, Noncurrent				$ 1,400,000,000		$ 1,400,000,000
Deferred tax liability				8,200,000		8,200,000
Temporary equity				$ 8,110,000		$ 8,110,000	$ 0
Shares of common stock covered by note hedges (shares) | shares		16,000
Additional warrant transaction (shares) | shares		16,000
Adjustment to number of shares of common stock covered by Bond Hedges and Warrant Transactions (in shares) | shares						20,000
Initial strike price of warrants (per share) | $ / shares				$ 94.94		$ 94.94
Debt Instrument, Convertible, Threshold Trading Days | day			20
Debt Instrument, Convertible, Threshold Consecutive Trading Days | day			30
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger			130.00%
Privately Negotiated Transaction
Debt Instrument [Line Items]
Payments for repurchase of common stock					101,000,000
Purchase From Accelerated Share Repurchase
Debt Instrument [Line Items]
Shares repurchased under the ASR					$ 1,400,000,000
Unsecured Debt [Member] | Unsecured Senior Notes due December 2027 [Member]
Debt Instrument [Line Items]
Principal amount of notes	$ 750,000,000
Stated interest rate (percent)	4.50%
Proceeds from 2027 notes, net of issuance costs	$ 741,000,000
Prior to September 1, 2017 [Member] | Unsecured Debt [Member] | Unsecured Senior Notes due December 2027 [Member]
Debt Instrument [Line Items]
Redemption price, as percentage of aggregate principal amount (percent)	100.00%
Upon Change of Control Prior to Maturity [Member] | Unsecured Debt [Member] | Unsecured Senior Notes due December 2027 [Member]
Debt Instrument [Line Items]
Redemption price, as percentage of aggregate principal amount (percent)	101.00%
Minimum | Senior Notes Due 2019
Debt Instrument [Line Items]
Debt Instrument, Convertible, Threshold Trigger Stock Price | $ / shares			$ 93.48
Common Stock
Debt Instrument [Line Items]
Settlement of convertible notes and hedges (shares) | shares				1,300		1,291

Debt - Credit Facility (Details

Debt - Credit Facility (Details) - Line of Credit	Jan. 07, 2015USD ($)	Dec. 31, 2018USD ($)
Line of Credit Facility [Line Items]
Credit facility term	5 years
Potential increase in revolving credit facility commitment	$ 250,000,000
Amount outstanding		$ 0
Consolidated leverage ratio (not more than)	3.5
Consolidated interest coverage ratio (not less than)	3
Letter of Credit
Line of Credit Facility [Line Items]
Unsecured credit facility maximum amount	$ 25,000,000
Swing Line Loans
Line of Credit Facility [Line Items]
Unsecured credit facility maximum amount	$ 10,000,000
LIBOR
Line of Credit Facility [Line Items]
Basis spread on LIBOR (percent)		1.10%
Minimum
Line of Credit Facility [Line Items]
Quarterly facility fee (percent)		0.125%
Minimum | LIBOR
Line of Credit Facility [Line Items]
Basis spread on LIBOR (percent)		1.00%
Maximum
Line of Credit Facility [Line Items]
Quarterly facility fee (percent)		0.20%
Maximum | LIBOR
Line of Credit Facility [Line Items]
Basis spread on LIBOR (percent)		1.30%

Derivative Financial Instrume_3

Derivative Financial Instruments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Cash flow hedge instrument term, maximum	12 months
Cumulative unrealized gain (loss) on cash flow derivative instruments in accumulated other comprehensive loss	$ (1)	$ 2.2

Derivative Financial Instrume_4

Derivative Financial Instruments (Schedule Of The Fair Values Of Derivative Instruments) (Details) - Cash flow hedging - Foreign currency - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Derivatives Designated as Hedging Instruments | Prepaid expenses and other current assets
Asset Derivatives
Derivative assets fair value	$ 708	$ 2,481
Derivatives Designated as Hedging Instruments | Accrued expenses and other current liabilities
Liability Derivatives
Derivative liabilities fair value	1,811	110
Derivatives Not Designated as Hedging Instruments | Prepaid expenses and other current assets
Asset Derivatives
Derivative assets fair value	56	17
Derivatives Not Designated as Hedging Instruments | Accrued expenses and other current liabilities
Liability Derivatives
Derivative liabilities fair value	$ 732	$ 704

Derivative Financial Instrume_5

Derivative Financial Instruments (Schedule Of Effect Of Derivative Instruments On Financial Performance) (Details) - Cash flow hedging - Foreign currency - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Derivatives Designated as Hedging Instruments
Derivative Instruments, Gain (Loss) [Line Items]
Amount of (Loss) Gain Recognized in Other Comprehensive Income (Loss) (Effective Portion)	$ (3,143)	$ 5,288
Derivatives Designated as Hedging Instruments | Operating expenses
Derivative Instruments, Gain (Loss) [Line Items]
Amount of (Loss) Gain Reclassified from Accumulated Other Comprehensive Loss (Effective Portion)	(699)	758
Derivatives Not Designated as Hedging Instruments | Other (expense) income, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivative	$ 7,062	$ (6,804)

Derivative Financial Instrume_6

Derivative Financial Instruments (Schedule Of Net Notional Foreign Currency Forward Contracts Outstanding) (Details) - Dec. 31, 2018 € in Thousands, ₩ in Thousands, ₨ in Thousands, ¥ in Thousands, ¥ in Thousands, £ in Thousands, kr in Thousands, SFr in Thousands, R$ in Thousands, $ in Thousands, $ in Thousands, $ in Thousands, $ in Thousands, $ in Thousands

KRW (₩)

GBP (£)

CHF (SFr)

AUD ($)

HKD ($)

NZD ($)

INR (₨)

CAD ($)

DKK (kr)

JPY (¥)

CNY (¥)

BRL (R$)

EUR (€)

SGD ($)

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Net notional foreign currency forward contracts outstanding

₩ 150,000

£ 14,100

SFr 19,450

$ 18,200

$ 20,600

$ 100

₨ 62,000

$ 2,350

kr 6,329

¥ 2,300,000

¥ 41,800

R$ 5500

€ 9,736

$ 13,500

Earnings Per Share (Net Income

Earnings Per Share (Net Income Per Share Basic And Diluted) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2014
Numerator:
Income from continuing operations					$ (283,889)	$ 126,720	$ 108,829	$ 70,325	$ 575,667	$ 21,985	$ 469,855
(Loss) income from discontinued operations, net of income taxes					0	0	0	(42,704)	0	(42,704)	66,257
Net income (loss)	$ 165,718	$ 158,857	$ 106,833	$ 144,259	$ (283,889)	$ 126,720	$ 108,829	$ 27,621	$ 575,667	$ (20,719)	$ 536,112
Denominator:
Denominator for basic earnings per share - weighted-average shares outstanding									136,030	150,779	155,134
Effect of dilutive employee stock awards									2,653	2,493	1,950
Effect of dilutive Convertible Notes									5,769	2,231	0
Effect of dilutive warrants									1,482	0	0
Denominator for diluted earnings per share - weighted-average shares outstanding									145,934	155,503	157,084
Basic earnings (loss) per share:
Income from continuing operations (USD per share)					$ (1.93)	$ 0.84	$ 0.72	$ 0.46	$ 4.23	$ 0.15	$ 3.03
(Loss) income from discontinued operations (USD per share)									0	(0.28)	0.43
Basic net earnings (loss) per share (USD per share)	$ 1.24	$ 1.18	$ 0.79	$ 1.04	(1.93)	0.84	0.72	0.18	4.23	(0.13)	3.46
Diluted earnings (loss) per share:
Income from continuing operations (USD per share)					(1.93)	0.82	0.70	0.44	3.94	0.14	2.99
(Loss) income from discontinued operations (USD per share)									0	(0.27)	0.42
Diluted net earnings (loss) per share (USD per share)	1.15	$ 1.08	$ 0.73	$ 0.99	$ (1.93)	$ 0.82	$ 0.70	$ 0.17	3.94	$ (0.13)	$ 3.41
Senior Notes Due 2019
Diluted earnings (loss) per share:
Strike price of warrants (in dollars per share)	94.94								94.94
Stated interest rate (percent)												0.50%
Convertible debt, conversion price (in dollars per share)	$ 71.68								$ 71.68

Comprehensive Income (Changes i

Comprehensive Income (Changes in Accumulated Other Comprehensive Loss by Component) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2017	$ (10,806)
Other comprehensive (loss) income before reclassifications	(4,043)
Amounts reclassified from accumulated other comprehensive loss	6,695
Other comprehensive income (loss)	2,652	$ 4,498	$ (177)
Balance at December 31, 2018	(8,154)	(10,806)
Foreign currency
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2017	(2,946)
Other comprehensive (loss) income before reclassifications	0
Amounts reclassified from accumulated other comprehensive loss	0
Other comprehensive income (loss)	0
Balance at December 31, 2018	(2,946)	(2,946)
Unrealized loss on available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2017	(6,666)
Other comprehensive (loss) income before reclassifications	(1,770)
Amounts reclassified from accumulated other comprehensive loss	5,996
Other comprehensive income (loss)	4,226
Balance at December 31, 2018	(2,440)	(6,666)
Unrealized gain (loss) on derivative instruments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2017	2,158
Other comprehensive (loss) income before reclassifications	(3,842)
Amounts reclassified from accumulated other comprehensive loss	699
Other comprehensive income (loss)	(3,143)
Balance at December 31, 2018	(985)	2,158
Other comprehensive loss on pension liability
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2017	(3,352)
Other comprehensive (loss) income before reclassifications	1,569
Amounts reclassified from accumulated other comprehensive loss	0
Other comprehensive income (loss)	1,569
Balance at December 31, 2018	$ (1,783)	$ (3,352)

Comprehensive Income (Reclassif

Comprehensive Income (Reclassifications out of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense), net										$ 8,373	$ (3,150)	$ 4,131
Operating expenses										(1,862,140)	(1,814,043)	(1,771,027)
Net income		$ (165,718)	$ (158,857)	$ (106,833)	$ (144,259)	$ 283,889	$ (126,720)	$ (108,829)	$ (27,621)	(575,667)	$ 20,719	$ (536,112)
Amount reclassified from Accumulated other comprehensive loss, net of tax
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income										6,695
Amount reclassified from Accumulated other comprehensive loss, net of tax | Unrealized net loss on available-for-sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense), net										5,996
Amount reclassified from Accumulated other comprehensive loss, net of tax | Unrealized net loss on cash flow hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Operating expenses	[1]									$ 699
[1]	Operating expenses amounts allocated to Research and development, Sales, marketing and services, and General and administrative are not individually significant.

Restructuring - (Restructuring

Restructuring - (Restructuring Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring	$ 16,725	$ 72,375	$ 67,401
Operational Initiatives for Cloud-based Subscription Business, Strategic Focus and Efficiencies
Restructuring Cost and Reserve [Line Items]
Restructuring	2,500	53,700	0
Operational Initiatives for Infrastructure Scalability and Cost Saving Efficiencies
Restructuring Cost and Reserve [Line Items]
Restructuring		8,100	0
November 2015 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring		1,900	44,500
January 2015 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring		$ 8,700	$ 24,000
Consolidation of Leased Facilities
Restructuring Cost and Reserve [Line Items]
Restructuring	$ 14,200

Restructuring - (Restructurin_2

Restructuring - (Restructuring Charges) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring and Related Activities [Abstract]
Employee severance and related costs	$ 2,507	$ 62,844	$ 41,054
Consolidation of leased facilities	14,218	9,718	28,857
Reversal of previous charges	0	(187)	(2,510)
Restructuring Charges	$ 16,725	$ 72,375	$ 67,401

Restructuring - (Activity in Re

Restructuring - (Activity in Restructuring Accruals) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring Reserve [Roll Forward]
Balance, beginning	$ 55,283
Restructuring charges	16,725	$ 72,375	$ 67,401
Payments	(26,913)
Balance, ending	$ 45,095	$ 55,283

Quarterly Financial Informati_3

Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Quarterly Financial Data [Abstract]
Net revenues	$ 801,870	$ 732,476	$ 742,365	$ 697,192	$ 777,857	$ 690,925	$ 693,227	$ 662,677	$ 2,973,903	$ 2,824,686	[1],[2]	$ 2,736,080	[1],[2]
Gross margin	689,019	628,559	633,616	588,906	655,918	584,988	583,915	560,219	2,540,100	2,385,040		2,331,191
Income from operations	202,471	164,779	145,147	165,563					677,960	570,997		560,164
Income from continuing operations					(283,889)	126,720	108,829	70,325	575,667	21,985		469,855
Loss from discontinued operations, net of tax					0	0	0	(42,704)	0	(42,704)		66,257
Net income	$ 165,718	$ 158,857	$ 106,833	$ 144,259	$ (283,889)	$ 126,720	$ 108,829	$ 27,621	$ 575,667	$ (20,719)		$ 536,112
Income (loss) from continuing operations (USD per share)					$ (1.93)	$ 0.84	$ 0.72	$ 0.46	$ 4.23	$ 0.15		$ 3.03
Loss from discontinued operations (USD per share)					0	0	0	(0.28)		(0.28)
Basic net earnings (loss) per share (USD per share)	$ 1.24	$ 1.18	$ 0.79	$ 1.04	(1.93)	0.84	0.72	0.18	4.23	(0.13)		3.46
Income (loss) from continuing operations (USD per share)					(1.93)	0.82	0.70	0.44	3.94	0.14		2.99
Loss from discontinued operations (USD per share)					0	0	0	(0.27)		(0.27)
Diluted net earnings (loss) per share (USD per share)	$ 1.15	$ 1.08	$ 0.73	$ 0.99	$ (1.93)	$ 0.82	$ 0.70	$ 0.17	$ 3.94	$ (0.13)		$ 3.41
[1]	As noted above, prior period amounts have not been adjusted under the modified retrospective method of adoption of therevenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenuerecognition standard.
[2]	Prior period amounts have not been adjusted under the modified retrospective method of adoption of the revenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenue recognition standard.

Valuation and Qualifying Acco_2

Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Allowance for doubtful accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning of Period		$ 3,420		$ 3,889		$ 6,241
Charged to Expense		3,586		3,917		954
Charged to Other Accounts		457	[1]	9	[1]	0
Deductions	[2]	3,829		4,395		3,306
Balance at End of Period		3,634		3,420		3,889
Allowance for returns
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning of Period		1,225		1,994		1,438
Charged to Expense		0		0		0
Charged to Other Accounts	[3]	1,561		4,890		2,088
Deductions	[4]	1,890		5,659		1,532
Balance at End of Period		896		1,225		1,994
Valuation allowance for deferred tax assets
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning of Period		76,789		14,156		16,673
Charged to Expense		0		0		0
Charged to Other Accounts	[5]	8,611		62,633		(2,517)
Deductions		0		0		0
Balance at End of Period		$ 85,400		$ 76,789		$ 14,156
[1]	Adjustments from acquisitions.
[2]	Uncollectible accounts written off, net of recoveries.
[3]	Charged against revenues.
[4]	Credits issued for returns.
[5]	Related to deferred tax assets on foreign tax credits, net operating loss carryforwards, and depreciation.