Ixia (XXIA) 10-K 1 Mar 17 2016 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2016	Feb. 21, 2017	Jun. 30, 2016
Document and Entity Information [Abstract]
Entity Registrant Name	Ixia
Document Type	10-K
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		82,867,065
Entity Public Float			$ 618,688,890
Amendment Flag	false
Entity Central Index Key	1,120,295
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Well-Known Seasoned Issuer	No
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 71,759	$ 52,472
Marketable securities	71,251	14,504
Accounts receivable, net	103,395	121,932
Inventories	28,657	33,289
Prepaid expenses and other current assets	29,711	44,384
Total current assets	304,773	266,581
Property and equipment, net	36,666	36,536
Intangible assets, net	65,677	103,660
Goodwill	338,873	338,873
Other assets	11,578	34,227
Total assets	757,567	779,877
Current liabilities:
Accounts payable	9,705	15,346
Accrued expenses and other	39,402	70,029
Deferred revenues	115,784	108,436
Term loan, net	5,048	3,045
Total current liabilities	169,939	196,856
Deferred revenues	30,861	22,117
Other liabilities	16,692	7,406
Term loan, net	28,538	34,487
Total liabilities	246,030	260,866
Commitments and contingencies (Note 10)
Shareholders’ equity:
Preferred stock, without par value; 1,000 shares authorized and none outstanding	0	0
Common stock, without par value; 200,000 shares authorized at December 31, 2016 and 2015; 82,604 and 80,805 shares issued and outstanding as of December 31, 2016 and 2015, respectively	209,475	201,087
Additional paid-in capital	243,356	225,432
Retained earnings	59,614	93,525
Accumulated other comprehensive loss	(908)	(1,033)
Total shareholders’ equity	511,537	519,011
Total liabilities and shareholders’ equity	$ 757,567	$ 779,877

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - shares	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares outstanding	0	0
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	82,604,000	80,805,000
Common stock, shares outstanding	82,604,000	80,805,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues:
Products		$ 311,203	$ 361,923	$ 325,455
Services		173,642	155,014	139,003
Total revenues		484,845	516,937	464,458
Costs and operating expenses:
Cost of revenues – products	[1],[2]	87,528	97,415	98,815
Cost of revenues – services	[2]	16,041	16,443	16,166
Research and development	[2]	102,534	113,443	115,156
Sales and marketing	[2]	161,604	155,211	151,765
General and administrative	[2]	58,975	68,925	66,475
Amortization of intangible assets	[2]	39,099	42,315	46,901
Acquisition and other related costs	[2]	785	656	3,277
Restructuring	[2]	(130)	(517)	10,310
Total costs and operating expenses	[2]	466,436	493,891	508,865
Income (loss) from operations		18,409	23,046	(44,407)
Interest income and other, net		310	(372)	(24)
Interest expense		(1,930)	(8,331)	(8,266)
Income (loss) before income taxes		16,789	14,343	(52,697)
Income tax expense (benefit)		50,700	8,392	(11,105)
Net (loss) income		$ (33,911)	$ 5,951	$ (41,592)
(Loss) earnings per share:
Basic (in dollars per share)		$ (0.42)	$ 0.07	$ (0.54)
Diluted (in dollars per share)		$ (0.42)	$ 0.07	$ (0.54)
Weighted average number of common and common equivalent shares outstanding:
Basic (in shares)		81,470	79,633	77,629
Diluted (in shares)		81,470	81,459	77,629
[1]	Cost of revenues – products excludes amortization of intangible assets related to purchased technologies of $25.3 million, $25.7 million, and $28.9 million for the years ended December 31, 2016, 2015, and 2014, respectively, which is included in Amortization of intangible assets.
[2]	Stock-based compensation included in:Cost of revenues – products$280 $315 $331Cost of revenues – services108 120 126Research and development6,489 6,625 6,843Sales and marketing5,944 4,730 5,624General and administrative5,886 7,186 3,595

Consolidated Statements of Ope5

Consolidated Statements of Operations (Parentheticals) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Total stock-based compensation		$ 18,707	$ 18,976	$ 16,519
Amortization of intangible assets	[1]	39,099	42,315	46,901
Cost of revenues – products
Total stock-based compensation		280	315	331
Cost of revenues – services
Total stock-based compensation		108	120	126
Research and development
Total stock-based compensation		6,489	6,625	6,843
Sales and marketing
Total stock-based compensation		5,944	4,730	5,624
General and administrative
Total stock-based compensation		5,886	7,186	3,595
Intangible assets related to purchased technologies
Amortization of intangible assets		$ 25,300	$ 25,700	$ 28,900
[1]	Stock-based compensation included in:Cost of revenues – products$280 $315 $331Cost of revenues – services108 120 126Research and development6,489 6,625 6,843Sales and marketing5,944 4,730 5,624General and administrative5,886 7,186 3,595

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (33,911)	$ 5,951	$ (41,592)
Unrealized gain (loss) on investments, net of tax	62	(56)	(74)
Foreign currency translation adjustment	63	(184)	(342)
Other comprehensive income (loss)	125	(240)	(416)
Comprehensive (loss) income	$ (33,786)	$ 5,711	$ (42,008)

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock - No Par	Additional Paid-in- Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balance at beginning of period (in shares) at Dec. 31, 2013		76,849
Balance at beginning of period at Dec. 31, 2013	$ 499,112	$ 178,347	$ 191,976	$ 129,166	$ (377)
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(41,592)			(41,592)
Change in unrealized gains and losses on investments, net of tax	(74)				(74)
Cumulative translation adjustment	(342)				(342)
Shares issued pursuant to stock incentive plans and employee stock purchase plan options (in shares)		1,726
Shares issued pursuant to stock incentive plans and employee stock purchase plan options	9,050	$ 9,050
Stock-based compensation	16,519		16,519
Stock award tax benefit (deficiency)	(1,582)		(1,582)
Balance at end of period (in shares) at Dec. 31, 2014		78,575
Balance at end of period at Dec. 31, 2014	481,091	$ 187,397	206,913	87,574	(793)
Increase (Decrease) in Stockholders' Equity
Net (loss) income	5,951			5,951
Change in unrealized gains and losses on investments, net of tax	(56)				(56)
Cumulative translation adjustment	(184)				(184)
Shares issued pursuant to stock incentive plans and employee stock purchase plan options (in shares)		2,230
Shares issued pursuant to stock incentive plans and employee stock purchase plan options	13,690	$ 13,690
Stock-based compensation	18,976		18,976
Stock award tax benefit (deficiency)	$ (457)		(457)
Balance at end of period (in shares) at Dec. 31, 2015	80,805	80,805
Balance at end of period at Dec. 31, 2015	$ 519,011	$ 201,087	225,432	93,525	(1,033)
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(33,911)			(33,911)
Change in unrealized gains and losses on investments, net of tax	62				62
Cumulative translation adjustment	63				63
Shares issued pursuant to stock incentive plans and employee stock purchase plan options (in shares)		2,506
Shares issued pursuant to stock incentive plans and employee stock purchase plan options	$ 15,240	$ 15,240
Repurchases of common stock (in shares)	(707)
Repurchases of common stock	$ (6,852)
Stock-based compensation	18,707		18,707
Stock award tax benefit (deficiency)	$ (783)		(783)
Balance at end of period (in shares) at Dec. 31, 2016	82,604	82,604
Balance at end of period at Dec. 31, 2016	$ 511,537	$ 209,475	$ 243,356	$ 59,614	$ (908)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net (loss) income		$ (33,911)	$ 5,951	$ (41,592)
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation		18,146	16,833	16,525
Amortization of intangible assets	[1]	39,099	42,315	46,901
Realized (gain) loss on sale of available-for-sale securities, net		(14)	31	(85)
Stock-based compensation		18,707	18,976	16,519
Deferred income taxes		37,196	(7,666)	(14,382)
Excess tax benefits from stock-based compensation		(662)	(758)	0
Amortization of deferred issuance costs		452	1,500	1,870
Amortization of investment premiums		51	80	63
Changes in operating assets and liabilities, net of the effect of acquisitions:
Accounts receivable, net		18,537	(22,404)	10,062
Inventories		(5,718)	4,365	(8,028)
Prepaid expenses and other current assets		5,955	(9,560)	(4,586)
Other assets		3,546	3,936	5,538
Accounts payable		(5,815)	(1,262)	(2,419)
Accrued expenses and other		(31,780)	34,129	(5,400)
Deferred revenues		16,092	12,337	13,853
Other liabilities		1,295	1	3,232
Net cash provided by operating activities		81,176	98,804	38,071
Cash flows from investing activities:
Purchases of property and equipment		(8,742)	(8,381)	(8,063)
Purchases of available-for-sale securities		(77,135)	(196,659)	(96,886)
Proceeds from available-for-sale securities		20,451	261,744	68,580
Purchases of other intangible assets		(1,116)	(867)	(771)
Proceeds from purchase price adjustments related to previous acquisitions		0	0	6,081
Payments in connection with acquisitions, net of cash acquired		0	0	(3,857)
Net cash (used in) provided by investing activities		(66,542)	55,837	(34,916)
Cash flows from financing activities:
Proceeds from borrowings under term loan		0	40,000	0
Repayments of debt		(3,500)	(201,663)	0
Debt issuance costs		(897)	(1,348)	0
Proceeds from exercise of stock options and employee stock purchase plan options		15,467	13,737	9,443
Cash paid for shares withheld for taxes		(227)	(47)	(393)
Repurchases of common stock		(6,852)	0	0
Excess tax benefits from stock-based compensation		662	758	0
Net cash provided by (used in) financing activities		4,653	(148,563)	9,050
Net increase in cash and cash equivalents		19,287	6,078	12,205
Cash and cash equivalents at beginning of year		52,472	46,394	34,189
Cash and cash equivalents at end of year		71,759	52,472	46,394
Cash paid (received) during the period for:
Interest		1,476	7,036	6,003
Income taxes		12,348	1,141	(1,446)
Supplemental disclosure of non-cash investing activities:
Purchased and unpaid property and equipment		560	1,440	1,088
Transfers of inventory to property and equipment		$ 10,350	$ 7,172	$ 10,464
[1]	Stock-based compensation included in:Cost of revenues – products$280 $315 $331Cost of revenues – services108 120 126Research and development6,489 6,625 6,843Sales and marketing5,944 4,730 5,624General and administrative5,886 7,186 3,595

Description of Business, Basis

Description of Business, Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Description of Business, Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements	Description of Business, Basis of Presentation, Significant Accounting Policies, and Recent Accounting Pronouncements Description of Business Ixia ("Ixia" or the "Company") was incorporated on May 27, 1997 as a California corporation. The Company provides application performance and security resilience solutions so that organizations can validate, secure, and optimize their physical and virtual networks. Enterprises, service providers, network equipment manufacturers, and governments worldwide rely on Ixia’s solutions to deploy new technologies and achieve efficient, secure ongoing operation of their networks. Ixia's product solutions consist of its high performance hardware platforms, software applications, and services, including warranty and maintenance offerings and professional services. The Company is headquartered in Calabasas, California with operations across the U.S. and the rest of the world. The Company's revenues are principally derived from shipments within the U.S. and to the Europe, Middle East and Africa ("EMEA"), and Asia Pacific regions. Basis of Presentation The accompanying consolidated financial statements for the years ended December 31, 2016 , 2015 , and 2014 have been prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP"). Use of Estimates In the normal course of preparing financial statements in conformity with GAAP, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Principles of Consolidation All subsidiaries are consolidated as they are 100% owned by us. All intercompany transactions and accounts are eliminated in consolidation. Significant Accounting Policies Cash and Cash Equivalents The Company considers all highly liquid investments with a maturity of three months or less at the date of purchase to be cash equivalents. Cash is carried at cost, which approximates fair value, and cash equivalents are carried at fair value. The Company generally invests funds that are in excess of current needs in high credit quality instruments such as money market funds. There are no restrictions on the use of cash and cash equivalents. Fair Value of Financial Instruments The Company's financial instruments, including cash, accounts receivable, and accounts payable are carried at cost, which approximates their fair values because of the short-term maturity of these instruments and the relative stability of interest rates. The fair values of the Company's cash equivalents, money market funds, U.S. treasury, government and agency debt securities, and corporate debt securities are based on quoted market prices as shown in its investment brokerage/custodial statements. Fair value is defined as the exit price, or the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants as of the measurement date. There is an established hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring the most observable inputs be used when available. Observable inputs are inputs market participants would use in valuing the asset or liability and are developed based on market data obtained from independent sources. Unobservable inputs are inputs that reflect the assumptions about the factors that market participants would use in valuing the asset or liability. Foreign Currency Forward Contracts The Company utilizes foreign currency forward contracts to hedge certain accounts receivable amounts that are denominated in Japanese Yen, Euros, and British Pounds. These contracts are cash flow hedges used to reduce the risk associated with exchange rate movements, as gains and losses on these contracts are intended to offset exchange losses and gains on underlying exposures. Foreign currency contracts are typically short-term in duration ranging from one to four months. The Company does not enter into foreign exchange forward contracts for speculative or trading purposes. In accordance with ASC 815, “Derivatives and Hedging,” the Company records all derivatives in the consolidated balance sheet as either assets or liabilities measured at fair value. The Company’s foreign currency contracts are generally not designated as hedges and any gains or losses on the movement in their fair values is recognized in the results of operations immediately. Foreign currency contracts are recorded at fair market values as a component of Prepaid expenses and other current assets in the consolidated balance sheet and the change in their fair value is recorded as a gain or loss in the consolidated statements of operations as a component of Interest income and other, net . As of December 31, 2016 , the Company held four open foreign currency forward contracts with a notional value of $3.9 million and a net fair value of approximately $7,000 . As of December 31, 2015 , the Company held three open foreign currency forward contracts with a notional value of $4.8 million and a net fair value of approximately $15,000 . During 2016 , net losses related to the change in fair value of such foreign currency forward contracts were approximately $54,000 . During 2015 and 2014 , net gains related to the change in fair value of such foreign currency forward contracts were approximately $208,000 and $531,000 , respectively. Investments in Marketable Securities The Company maintains a portfolio of cash equivalents and investments in a variety of fixed and variable rate securities, including U.S. government and federal agency securities, corporate debt securities, and money market funds. The primary objective of the Company's investment activities is to maintain the safety of principal and preserve liquidity while maximizing yields without significantly increasing risk. The Company does not enter into investments for trading or speculative purposes. The Company determines the appropriate classification of investments in marketable securities at the time of purchase. Accretion and amortization of purchase discounts and premiums are included in Interest income and other, net . Available-for-sale securities are stated at fair value. The net unrealized gains or losses on available-for-sale securities are reported as a separate component of accumulated other comprehensive income or loss, net of tax. The specific identification method is used to compute realized gains and losses on marketable securities. In 2016 , 2015 , and 2014 , gross realized gains and losses were not significant. The Company regularly reviews its investment portfolio to determine if any security is other-than-temporarily impaired, which would require it to record an impairment charge in the period any such determination is made. In making this judgment, the Company evaluates, among other things, the duration and extent to which the fair value of a security is less than its cost, and its intent and ability to sell, or whether it will more likely than not be required to sell, the security before recovery of its amortized cost basis. The Company has evaluated its investments as of December 31, 2016 and has determined that no investments with unrealized losses are other-than-temporarily impaired. The Company does not intend to sell any investments whose fair value is currently below cost, and it is not more likely than not that it would be required to sell these investments, before recovery of the amortized cost basis, which may be at maturity. It is possible that the Company could recognize future impairment charges on the investment securities it currently owns if future events, new information, or the passage of time cause the Company to believe that a decline in the carrying value of its securities is other-than-temporary. The Company will continue to review and analyze these securities for triggering events each reporting period. See Note 6 for additional information. Accounts Receivable and Allowance for Doubtful Accounts Trade accounts receivable are recorded at the invoiced amount. The allowance for doubtful accounts is based on the Company's best estimate of the amount of probable credit losses in existing accounts receivable. The Company reviews the allowance for doubtful accounts, and provisions are made upon a specific review of all significant past due receivables. For those receivables not specifically reviewed, provisions are provided at a general rate that considers historical write-off experience and other qualitative factors. Account balances are charged off against the allowance when the Company believes it is probable the receivable will not be recovered. Inventories Inventories are goods held for sale in the normal course of business. Inventories are stated at the lower of cost (first-in, first-out) or market. The inventory balance consists of raw materials, work in process (“WIP”), and finished goods. Raw materials include low level components, many of which are purchased from vendors, WIP consists of partially assembled products, and finished goods are products that are ready to be shipped to end customers. Consideration is given to inventory shipped and received near the end of a period, and the transaction is recorded when transfer of title occurs. The Company evaluates inventory for excess and obsolescence and adjusts its carrying amount to net realizable value based on inventory that is obsolete or in excess of current demand. Property, Plant, and Equipment Property, plant, and equipment are stated at cost less accumulated depreciation. Depreciation of the Company's computer software and equipment is computed using the straight-line method based upon the estimated useful lives of the applicable assets, ranging from three to five years. Building and leasehold improvements are amortized over the lesser of their estimated useful lives or the remaining lease term. Useful lives are evaluated periodically by management in order to determine recoverability in light of current technological conditions. Property, plant, and equipment also include the cost of the Company's products used for research and development which are classified as development equipment and are depreciated over five years to research and development. The Company also capitalizes and depreciates over a two -year period costs of its products used for sales and marketing activities, including product demonstrations for potential customers, which is included in Sales and marketing in the consolidated statements of operations. Repair and maintenance costs are charged to expense as incurred while renewals and improvements are capitalized. Upon the sale or retirement of property, plant, and equipment, the accounts are relieved of the cost and the related accumulated depreciation, with any resulting gain or loss included in the consolidated statements of operations. Goodwill The Company records goodwill as the difference, if any, between the aggregate consideration paid for an acquisition and the fair value of the acquired net tangible and identifiable intangible assets. The Company evaluates the recoverability of its goodwill on an annual basis or if events or changes in circumstances indicate that impairment in the value of goodwill recorded on its balance sheet may exist. The Company has determined that it has one reporting unit for goodwill impairment testing purposes. The fair value of the Company’s reporting unit is determined using the market capitalization of Ixia, which considers the observed market price of the Company’s publicly-traded equity securities on the impairment test date. The fair value of the Company’s reporting unit is then compared to the carrying amount of the Company’s reporting unit under “step 1” of the impairment testing model. If the carrying value of the reporting unit exceeds its fair value, then the fair value of goodwill is determined and compared to its carrying value under “step 2.” Impairment losses are recorded to the extent that the carrying value of the goodwill exceeds its estimated fair value. The Company completed its annual goodwill impairment test of its single reporting unit as of December 31, 2016 and determined that there was no impairment. Intangible Assets Intangible assets consist primarily of acquired intellectual property and other long-lived assets, such as purchased technology, customer relationships, service agreements, trade names, and non-compete agreements. Acquired intangible assets with finite lives are amortized over their estimated useful lives and reflected in the Amortization of intangible assets line item on the consolidated statements of operations. Intangible assets with finite lives are tested for impairment whenever events or circumstances indicate that the carrying amount of an asset (asset group) may not be recoverable. Circumstances which could trigger a review include, but are not limited to: significant adverse change in the extent or manner in which the intangible asset is being used; significant adverse changes in the business climate or legal factors; current period cash flow or operating losses combined with a history of losses or a forecast of continuing losses associated with the use of the asset; or a current expectation that the asset will more likely than not be sold or disposed of significantly before the end of its estimated useful life. An impairment loss is recognized when the carrying amount of an asset exceeds the estimated undiscounted cash flows used in determining the fair value of the asset. The amount of the impairment loss recorded is calculated as the excess of the asset’s carrying value over its fair value. Fair value is generally determined using a discounted cash flow analysis and may involve the use of significant estimates and assumptions, some of which may be based in part on historical experience, forecasted information, and discount rates. No such impairment charges were recorded during the years ended December 31, 2016 , 2015 , and 2014 . Litigation The Company accrues for losses when the loss is deemed probable and the liability can reasonably be estimated. Where a liability is probable and there is a range of estimated loss with no best estimate in the range, the Company records the minimum estimated liability related to the claim. As additional information becomes available, the Company assesses the potential liability related to its pending litigation and revises its estimates. See Note 10 for additional information. Product Warranty The Company generally provides an initial standard warranty ( 90 -day or 12 -month periods) on its hardware products after product shipment and accrues for estimated future warranty costs based on actual historical experience and other relevant data, as appropriate, at the time product revenue is recognized. All product warranty expenses associated with the Company's initial standard warranty is reflected within Cost of revenues-products in the accompanying consolidated statements of operations. Accrued product warranty costs are included as a component of Accrued expenses and other in the accompanying consolidated balance sheets. Activity in the product warranty liability account for the years presented is as follows (in thousands): December 31, December 31, December 31, Balance at beginning of year $ 538 $ 716 $ 646 Current year provision 1,972 2,072 1,759 Expenditures (2,193 ) (2,250 ) (1,689 ) Balance at end of year $ 317 $ 538 $ 716 Revenue Recognition Sales of the Company's network test hardware products primarily consist of traffic generation and analysis hardware platforms containing multi-slot chassis and interface cards. The Company's primary network test hardware platform is enabled by its operating system software that is essential to the functionality of the hardware platform. Sales of the Company's network visibility hardware products typically include an integrated, purpose-built hardware appliance with essential, proprietary software. The Company's software products consist of a comprehensive suite of technology-specific applications for certain of its network test hardware platforms. The Company's software products are typically installed on and work with these hardware products to further enhance the core functionality of the overall network test system, although some of its software products can be operated independently from its network test platforms. The Company's service revenues primarily consist of technical support, warranty, and software maintenance services related to its network test and visibility hardware and software products. Many of the Company's products include up to one year of these services with the initial product purchase, and its customers may separately purchase extended services for annual or multi-year periods. The Company's technical support, warranty, and software maintenance services include assistance with the set-up, configuration, and operation of its products, repair or replacement of defective products, bug fixes, and unspecified when and if available software upgrades. For certain network test products, the Company's technical support and software maintenance service revenues also include its Application and Threat Intelligence ("ATI") subscription service, which provides a comprehensive suite of application protocols, software updates, and technical support. The ATI subscription service provides full access to the latest security attacks and application updates for use in real-world test and assessment scenarios. The Company's customers may purchase the ATI subscription service for annual or multi-year periods. Service revenues also include training and other professional services. As the Company's systems typically include hardware and software products and the related services, the Company recognizes its revenue in accordance with authoritative guidance on both hardware and software revenue recognition. Furthermore, in accordance with the current revenue recognition guidance, the Company's hardware platform and certain other products that include both tangible products and software elements that function together to deliver the tangible product’s essential functionality have been scoped out of software revenue recognition guidance, and therefore these products are accounted for as hardware products for revenue recognition purposes. The Company recognized revenue for hardware and software products and related services based on the following four criteria: whether (i) evidence of an arrangement exists, which is typically in the form of a customer purchase order; (ii) delivery has occurred (i.e., risks and rewards of ownership have passed to the customer); (iii) the sales price is fixed or determinable; and (iv) collectability is deemed reasonably assured (or probable for software-related deliverables). Provided that the above criteria are met, revenue from hardware and software product sales is typically recognized upon shipment, and service revenues are recognized as the services are provided or completed. The Company recognizes service revenues from its initial and separately purchased technical support, warranty, and software maintenance arrangements on a straight-line basis over the applicable contractual period. The Company's systems are generally fully functional at the time of shipment and do not require the Company to perform any significant production, modification, customization, or installation after shipment. If an arrangement includes acceptance provisions based on customer specified criteria for which it cannot reliably demonstrate that the delivered product meets all the specified criteria, revenue is deferred until the earlier of the receipt of written customer acceptance or the expiration of the acceptance period. In addition, the arrangements generally do not include any provisions for cancellation, termination, or refunds. Multiple Element Arrangements and Allocation of Value The Company's sales arrangements with its customers typically include a combination of its hardware and software products, as well as the related technical support, warranty, and software maintenance services of these products, and therefore are commonly referred to as multiple element arrangements. When sales arrangements involve hardware and software elements, the Company uses a two-step process to allocate value to each element in the arrangement: (1) The total arrangement fee is allocated to the separate non-software deliverables (e.g., chassis, interface cards, and software post contract customer support and maintenance (“PCS”) related to the Company's operating system software that is essential to the functionality of its hardware platform) and the software-related deliverables as a group (e.g., application software and software PCS) based on a relative selling price (“RSP”) method applied to all elements in the arrangement using the selling price hierarchy in the revenue recognition guidance as discussed below; and (2) The value assigned to the software group for the software deliverables is then allocated to each software element based on the residual method, whereby value is allocated first to the undelivered elements, typically PCS, and the residual portion of the value is then allocated to the delivered elements (typically the software products) and recognized as revenue, provided all other revenue recognition criteria discussed above have been met. The fair value of an element must be based on vendor specific objective evidence (“VSOE”) of the selling price, which typically only exists for technical support, warranty, and software maintenance services as discussed below. Under the RSP method, the selling price to be used in the allocation of the total arrangement fee to each of the elements, or deliverables, is based on a selling price hierarchy, where the selling price for each element is based on (i) VSOE, if available; (ii) third-party evidence (“TPE”), if available and VSOE is not available; or (iii) the best estimate of selling price (“BESP”), if neither VSOE nor TPE are available. The Company determines VSOE of fair value based on a bell-shaped curve approach, considering the actual sales prices charged to customers when the same element is sold separately, provided it is substantive. All of the Company's products are sold as multiple element arrangements and not sold separately, as its products include an initial period (generally 90 -day or 12 -month periods) of free technical support, warranty, and software maintenance services. Accordingly, the Company has not established VSOE for nearly all of its products. On a regular basis, the Company separately sells extended technical support, warranty, and software maintenance services upon the expiration of the initial contractual periods included in an initial sales arrangement and have been able to establish VSOE for its technical support, warranty, and software maintenance services. The Company generally is not able to determine TPE for its products or services because its products are not interchangeable with those of its competitors. Furthermore, the Company is unable to reliably determine competitive selling prices when the applicable competitive products are sold separately. As such, the Company uses BESP for all of its products and services when allocating the total consideration of multiple element arrangements to each of the deliverables under step one of the allocation process described above except for its technical support, warranty, and software maintenance services where it uses VSOE. The Company determines BESP for a product or service by considering multiple factors including, analyzing historical sales price data for stand-alone and bundled arrangements, published price lists, geographies, and customer types. The Company's estimate of BESP used in its allocation of arrangement consideration requires significant judgment, and the Company reviews these estimated selling prices on a quarterly basis. The allocation of value to each deliverable in a multiple element arrangement is completed at the inception of an arrangement, which is typically the receipt of a customer purchase order. The allocated value of each non-software deliverable is then recognized as revenue when each element is delivered, provided all of the other revenue recognition criteria discussed above have been met. For software deliverables, the total software group allocation (or total arrangement consideration for customer orders that include only software products and related services) is allocated based on the residual method which requires that the Company first allocates value to the undelivered element at VSOE of the selling price of the undelivered element and the remaining portion of the arrangement fee is allocated to the delivered elements. As the Company does not sell its software products without technical support, warranty, and software maintenance services, it is unable to establish VSOE for its software products, and therefore uses the residual method under the software revenue recognition guidance to allocate the software group (or arrangement) value to each software deliverable. Under the residual method, the software group (or arrangement) value is allocated first to the undelivered elements, typically technical support, warranty, and software maintenance services based on VSOE, and the residual portion of the value is then allocated to the delivered elements (typically the software products) and recognized as revenue, provided all other revenue recognition criteria discussed above have been met. If VSOE cannot be established for an undelivered element within the software group (or arrangement), the value allocated to the software group (or arrangement) is deferred until the earlier of (i) delivery of all elements (other than technical support, warranty, and software maintenance services) or (ii) establishment of VSOE of the undelivered element(s). If the only undelivered element(s) relates to a service for which VSOE has not been established, the entire allocated value of the software group (or arrangement) is recognized as revenue over the longer of the service or contractual period of the technical support, warranty, and software maintenance services. VSOE of fair value typically only exists for the Company’s technical support, warranty, and software maintenance services (“Support”). VSOE of fair value is established using the bell-shaped curve approach for a subgroup when a substantial majority (generally greater than 75% ) of the transactions are priced within a reasonably narrow range (generally plus or minus 15% from the list price, which approximates the median). On a regular basis, the Company separately sells Support upon the expiration of the initial contractual periods included in an initial sales arrangement (“Support Renewals”). The population of Support Renewals is used in the bell-shaped curve approach to establish VSOE of fair value of Support and consists of actual sales prices charged to customers for Support Renewals and includes only Support Renewals sold separately on a stand-alone basis. The Company reviews these stand-alone sales of its Support Renewals for VSOE of fair value of its Support on a quarterly basis (“VSOE Analysis”). The Company’s pricing for Support Renewal transactions is generally based on a percentage of the Company’s list price for the product for which the Support Renewal is being purchased. When pricing conditions vary significantly, the Company further stratifies the population of stand-alone sales of its Support Renewals based on Support Renewal pricing conditions and separately analyzes these subgroups of Support Renewal transactions. The Company’s Support Renewal pricing conditions consist of the underlying product type, product family, customer type, and the geographic region in which the sale is made. Sales to Distributors The Company uses distributors and resellers to complement its direct sales and marketing efforts in certain markets and/or for certain products. Due to the broad range of features and options available with the Company's hardware and software products, distributors and resellers generally do not stock the Company's products and typically place orders with the Company after receiving an order from an end customer. These distributors and resellers receive business terms of sale similar to those received by the Company's other customers; and payment to the Company is not contingent on sell-through to and receipt of payment from the end customer. As such, for sales to distributors and resellers, the Company recognizes revenue when the risks and rewards of ownership have transferred to the distributor or reseller provided that the other revenue recognition criteria noted above have been met. Cost of Revenues The Company's cost of revenues related to the sale of its hardware and software products includes materials, payments to third party contract manufacturers, royalties, and salaries and other expenses related to its manufacturing and supply operations personnel. The Company outsources the majority of its manufacturing operations. Accordingly, a significant portion of the Company's cost of revenues related to its products consists of payments to its contract manufacturers. Cost of revenues related to the provision of services includes salaries and other expenses associated with technical support services and the cost of extended warranty and maintenance services. Cost of revenues does not include the amortization of purchased technology related to the Company's acquisitions of certain businesses, product lines, and technologies of $25.3 million , $25.7 million , and $28.9 million for the years ended December 31, 2016 , 2015 , and 2014 , respectively, which are included the Amortization of intangible assets line item on the Company's consolidated statements of operations. Shipping and Handling Costs Shipping and handling costs are reported in Sales and marketing expenses in the Company's consolidated statements of operations. For the years ended December 31, 2016 , 2015 , and 2014 the Company recorded shipping and handling costs of $1.4 million , $1.3 million , and $1.7 million , respectively. Research and Development Research and development expenses consist primarily of salaries and other personnel costs related to the design, development, testing, and enhancement of the Company's products. Costs related to research and development activities, including those incurred to establish the technological feasibility of a software product, are expensed as incurred. If technological feasibility is established, all development costs incurred until general product release are subject to capitalization. To date, establishment of technological feasibility of the Company's products and general release have substantially coincided. As a result, the Company has not capitalized any development costs. Software Developed for Internal Use The Company capitalizes costs of software, consulting services, hardware, and payroll-related costs incurred to purchase or develop internal-use software in accordance with the authoritative guidance on accounting for the costs of computer software developed or obtained for internal use. Internally developed software includes enterprise-level business software that the Company is customizing to meet its specific operational needs. To date, internal costs incurred to purchase or develop software for internal use have not been significant. Internally developed software is amortized over five years. Advertising Advertising costs are expensed as incurred. Advertising costs included in sales and marketing expenses in the Company's consolidated statements of operations were $3.6 million , $2.4 million , and $2.6 million for the years ended December 31, 2016 , 2015 , and 2014 , respectively. Acquisition and Other Related Costs Acquisition and other related costs are expensed as incurred and consist primarily of transaction and integration related costs such as success-based banking fees, professional fees for legal, accounting, tax, due diligence, valuation, and other related services, change in control payments, amortization of deferred compensation, consulting fees, required regulatory costs, certain employee, facility, and infrastructure transition costs, and other related expenses. The Company expects its acquisiti

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2016
Business Combinations [Abstract]
Acquisitions	Acquisitions Net Optics, Inc. On December 5, 2013 , the Company completed its acquisition of all of the outstanding shares of common stock and all other equity interests of Net Optics. Net Optics is a leading provider of total application and network visibility solutions. With this acquisition, the Company has expanded its product portfolio, strengthened its service provider and enterprise customer base, and broadened its sales channel and partner programs. In addition, the Company has realized certain operational synergies and has leveraged Net Optics’ existing sales channels, partner relationships and assembled workforce, including Net Optics' experienced product development team in Santa Clara, California and its global sales force. These factors, among others, contributed to a purchase price in excess of the estimated fair value of Net Optics’ net identifiable assets acquired (see summary of net assets below) and as a result, the Company has recorded goodwill in connection with this transaction. The aggregate purchase price totaled $187.4 million , and reflects certain post-closing adjustments, related to the final determination of the Net Optics’ closing working capital under the purchase agreement and the final amount of the tax reimbursements due to the sellers that were determined based upon the filing of certain tax returns. The acquisition was funded from the Company's existing cash and sale of investments. Acquisition and other related costs, including integration activities, related to the Net Optics' acquisition were insignificant for the year ended December 31, 2016 , and were $663,000 for the year ended 2015 . These acquisition and other related costs have been expensed as incurred and have been included within the Acquisition and other related costs line item on the Company's consolidated statements of operations. During the first quarter of 2014 , the Company reduced its aggregate purchase price for Net Optics from $193.8 million to $187.7 million due to a measurement period adjustment to finalize certain post-closing adjustments, including the net working capital calculation. The finalization of the net working capital calculation resulted in a decrease to the aggregate purchase price of $6.1 million and a corresponding reduction to goodwill. This adjustment was applied retrospectively to the acquisition date (i.e., December 5, 2013 ). The Company also recorded a measurement period adjustment to finalize the previous purchase accounting estimates resulting from an update to the tax basis of certain intangible assets. This resulted in an increase to deferred tax assets of $26.9 million and a corresponding decrease to goodwill, which were retrospectively adjusted to the acquisition date (i.e., December 5, 2013 ). These measurement period adjustments are reflected in the table below. During the fourth quarter of 2014 , the Company further reduced its aggregate purchase price for Net Optics from $187.7 million to $187.4 million due to a measurement period adjustment to finalize certain post-closing adjustments, including the final amount of the tax reimbursements due to the sellers that were determined upon the filing of certain tax returns. The adjustment reduced the value of the Company's accrued expenses and other liabilities and goodwill balances by approximately $341,000 . As these changes were not material, the Company did not recast its prior period financial statements for such changes. The below table reflects these changes. The following table summarizes the final allocation of the purchase price to the estimated fair values of the assets acquired and liabilities assumed at the date of acquisition (in thousands): Cash and cash equivalents $ 1,967 Accounts receivable 9,253 Inventories 6,543 Prepaid and other assets 1,742 Fixed assets, 2,976 Deferred tax asset 26,915 Identifiable intangible assets 72,858 Goodwill 78,727 Total assets acquired 200,981 Accounts payable, accrued expenses and other liabilities (8,440 ) Deferred revenues (5,170 ) Net assets acquired $ 187,371 The identifiable intangible assets of $72.9 million consist of $50.0 million of acquired technology, $15.8 million of customer relationships and related service agreements, $3.7 million related to non-compete agreements, $3.0 million for the trade name, and approximately $358,000 of other identifiable intangible assets. The fair values of the identifiable intangible assets have been estimated using the income approach, which includes the discounted cash flow and relief-from-royalty methods. These intangible assets will be amortized using a straight-line method over their expected useful lives ranging from four months to seven years. The goodwill recorded in connection with this transaction is tax deductible for U.S. income tax purposes.

Debt

Debt	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Debt	Debt Senior Secured Credit Agreements 2015 Credit Agreement On March 2, 2015 , the Company entered into an amended and restated credit agreement (as amended to date, the “Credit Agreement”) by and among the Company, as borrower, certain of the Company’s wholly owned direct and indirect subsidiaries, as guarantors, Silicon Valley Bank, as administrative agent, swingline lender and letter of credit issuer, and the other lenders party thereto (Silicon Valley Bank and the other lenders from time to time party thereto hereinafter collectively referred to as the “Lenders”). The Credit Agreement amended and restated the Company's prior credit agreement dated as of December 21, 2012, as amended, by and among the Company, the guarantors, Silicon Valley Bank, as administrative agent, swingline lender, and letter of credit issuer (as successor to Bank of America, N.A. in such capacities), and the other lenders party thereto. The Credit Agreement originally provided for a (i) term loan (the “Term Loan”) in the aggregate principal amount of $40 million and (ii) revolving credit facility (the “Revolving Credit Facility” and, together with the Term Loan, the “Credit Facility”) in an aggregate amount of up to $60 million , with sub-limits of $25 million for the issuance of standby letters of credit and $15 million for swingline loans. On September 30, 2015 , the Company entered into an amendment to the Credit Agreement which, among other modifications, increased the commitments under the Revolving Credit Facility to an aggregate amount of up to $75 million . On January 25, 2016 , the Company entered into an amendment to the Credit Agreement which, among other modifications, (i) increased the commitments under the Revolving Credit Facility to an aggregate amount of up to $150 million and (ii) extended the maturity date of the Revolving Credit Facility from February 15, 2018 to February 15, 2020 . The maturity date of the Term Loan is February 15, 2018 . The aggregate amount available under the Revolving Credit Facility is, upon the Company's request and subject to the receipt of increased commitments from the Lenders or additional lenders, subject to increase by an aggregate amount of up to $100 million . The Company is permitted to prepay outstanding loans under the Credit Facility at any time without premium or penalty. The Company may re-borrow amounts under the Revolving Credit Facility, but the Company may not re-borrow amounts that it repays or prepays under the Term Loan. Debt issuance costs were approximately $2.2 million , which were capitalized to deferred issuance costs and are being amortized to interest expense over the term of the Revolving Credit Facility. During the years ended December 31, 2016 and 2015 , amortization recorded to interest expense pertaining to deferred issuance costs was approximately $452,000 and $376,000 , respectively. There was no amortization recorded to interest expense pertaining to deferred issuance costs for the year ended 2014 . The Term Loan required quarterly repayments of $500,000 for the first four quarters and requires repayments ranging from $1.0 million to $1.5 million for the quarters thereafter through December 31, 2017 . The remaining principal balance will be due and payable on the maturity date of the Term Loan (i.e., February 15, 2018 ). The Company’s and the guarantors’ obligations under the Credit Agreement are secured by (i) a first priority perfected security interest in substantially all existing and after acquired tangible and intangible personal property of the Company and the guarantors and (ii) the pledge by the Company and the guarantors of (a) all outstanding equity securities of their existing and future domestic subsidiaries, including, in the case of the Company, the outstanding equity securities of each of the guarantors, and (b) 65% of the outstanding equity securities of their existing and future respective first-tier foreign subsidiaries, including, in the case of Catapult Communications Corporation (one of the Company's wholly owned domestic subsidiaries), 65% of the outstanding equity securities of Ixia Technologies International Limited, a company organized under the laws of Ireland. Interest rates for the Revolving Credit Facility and for the Term Loan are set, at the Company’s option, at a rate per annum based on the Eurodollar rate or a defined base rate. Prior to September 30, 2015 , the interest rates were 4.25% above the Eurodollar rate or 3.25% above the defined base rate. After September 30, 2015 , the interest rates for both the Term Loan and the Revolving Credit Facility range from 2.0% to 3.0% above the Eurodollar rate for Eurodollar-based borrowings and from 1.0% to 2.0% above the defined base rate for base rate borrowings, in each case depending on the Company’s leverage ratio. The Company is also required to pay a quarterly commitment fee, ranging from 0.30% to 0.50% per annum, on the undrawn portion of the Revolving Credit Facility. Letter of credit fees accrue based on the daily amount available to be drawn under outstanding letters of credit and range from 2.0% to 3.0% , depending on the Company’s leverage ratio. Swingline loans bear interest at the defined base rate plus the applicable margin for loans under the Revolving Credit Facility based on the defined base rate. If the Company defaults under the Credit Agreement, the Lenders may increase the interest rate(s) to 2.0% more than the rate(s) otherwise applicable. The weighted average interest rate applicable to the Term Loan for the year ended December 31, 2016 was 2.57% . As of December 31, 2016 , the interest rate applicable to the amount outstanding under the Term Loan was 2.61% . The Credit Agreement requires the Company to comply with certain covenants, including maintaining (i) a fixed charge coverage ratio (as defined in the Credit Agreement) of not less than 1.25 to 1.00 and (ii) a consolidated total leverage ratio (as defined in the Credit Agreement), of not greater 3.25 to 1.00 through June 30, 2018 , and 3.00 to 1.00 thereafter, in each case measured quarterly on a trailing 12 month basis. The Credit Agreement contains reporting covenants typical for transactions comparable to the Credit Facility, including covenants to furnish the lenders with financial statements, business plans, annual budgets, and other financial and business information and with notice of certain material events and information regarding collateral. The Credit Agreement also contains customary affirmative covenants, including covenants relating to the payment of obligations, preservation of the existence of and registrations for patents, trademarks, trade names and copyrights, maintenance of properties and insurance, compliance with laws and material contractual obligations, books and records, inspection rights, use of proceeds, addition of subsidiary guarantors, and security for the Credit Facility. The Credit Agreement contains customary negative covenants, including restrictions relating to liens and additional indebtedness, investments, mergers, liquidations and other fundamental changes, the sale and other disposition of properties and assets, restricted payments, changes in lines of business, transactions with affiliates, entering into certain burdensome agreements, and use of proceeds. The Credit Agreement permits the Company to fund cash acquisitions in an aggregate amount of up to $200 million , subject to certain limitations, including the requirement that, after giving effect to an acquisition, the Company’s available liquidity, as defined in the Credit Agreement, exceeds $50 million . The Credit Agreement provides for customary events of default, including the non-payment of amounts due, failure to perform under covenants, breaches of representations and warranties, cross-defaults relating to certain indebtedness, institution of insolvency proceedings, inability to pay debts as they become due, entry of certain judgments, events relating to the Employee Retirement Income Security Act of 1974, as amended, invalidity of loan documents, change of control events, and ineffectiveness of subordination provisions. The occurrence of an event of default may result in the acceleration of all outstanding obligations under the Credit Agreement and in an increase in the applicable interest rate(s) as described above. Unsecured Convertible Senior Notes On December 7, 2010 , the Company issued $200 million in aggregate principal amount of 3.00% Convertible Senior Notes (the “Notes”) due December 15, 2015 unless earlier repurchased or converted. The unsecured Notes were governed by the terms of an indenture dated December 7, 2010 between the Company and Wells Fargo Bank, N.A., as trustee (the “Indenture”). In July 2015 , the Company repurchased $65.0 million in aggregate principal amount of the Notes in a privately negotiated transaction for an aggregate cash purchase price of approximately $65.2 million plus accrued interest up to the date of repurchase in the aggregate amount of approximately $119,000 . In December 2015 , the remaining outstanding Notes in the aggregate principal amount of $135.0 million matured, and the Company repaid the Notes, together with the accrued interest in the aggregate amount of approximately $2.0 million , in full. Amortization of deferred issuance costs recorded to interest expense was $1.3 million and $1.2 million during the years ended December 31, 2015 and December 31, 2014 , respectively.

Restructuring Costs

Restructuring Costs	12 Months Ended
	Dec. 31, 2016
Restructuring and Related Activities [Abstract]
Restructuring Costs	Restructuring Costs During the year ended December 31, 2016 , the Company recorded net restructuring credits of $130,000 , consisting of restructuring charges of $0.2 million and restructuring credits of $0.3 million . Net restructuring credits recorded during the year ended December 31, 2016 consisted of recoveries relating to a favorable lease buyout in the current year related to costs previously charged to the Restructuring line item in the consolidated statements of operations. During the year ended December 31, 2015 , the Company recorded net restructuring credits of $517,000 , consisting of restructuring charges of $143,000 and restructuring credits of $660,000 . Net restructuring credits recorded during the year ended December 31, 2015 included recoveries in the amount of $371,000 relating to a favorable lease buyout and $382,000 relating to the receipt of proceeds from an insurance settlement related to costs previously charged to the Restructuring line item in the consolidated statements of operations. During the year ended December 31, 2014 , the Company recorded restructuring charges of $10.3 million , primarily related to the Net Optics Restructuring and the 2014 Corporate Restructuring, as described below. The Company’s restructuring charges include severance and other employee termination costs, lease termination costs, and other related costs, and are reported in the Restructuring line item in its consolidated statements of operations. The timing of associated cash payments depend upon the type of restructuring charge and can extend over multiple periods. During the first quarter of 2014 , the Company's management approved, committed to, and initiated a plan to restructure its operations following its December 5, 2013 acquisition of Net Optics (“Net Optics Restructuring”). The Net Optics Restructuring included a net reduction in force of approximately 45 positions (primarily impacting research and development personnel in Israel and Santa Clara, California), which represented approximately 2.3% of the Company's worldwide work force at that time. During 2014 , the Company recognized total restructuring costs of $3.5 million , of which $2.0 million related to employee termination benefits consisting of severance and other related employee costs, $1.2 million related to costs required to terminate its lease in Israel, and approximately $316,000 for other related costs. The Net Optics Restructuring was substantially completed by the second quarter of 2014, and no significant further charges are expected. During the third quarter of 2014 , the Company's management approved, committed to, and implemented a company-wide restructuring initiative (“2014 Corporate Restructuring”) to restructure its operations to better align the Company’s operating costs with its business opportunities. The restructuring included a reduction in force of approximately 96 positions across multiple business functions, which represented approximately 5% of the Company's worldwide work force at that time. During 2014 , the Company recognized total restructuring charges of $6.1 million , of which $4.1 million related to expenses for employee termination benefits, $1.8 million was associated with facility related charges in Austin, Santa Clara, India, and Romania, and approximately $181,000 was recognized for other related costs. The 2014 Corporate Restructuring was substantially completed by the fourth quarter of 2014 , and no significant further charges are expected. Activities related to the Company's restructuring plans are as follows (in thousands): Restructuring Prior to 2014 Net Optics Restructuring 2014 Corporate Restructuring Other Restructuring Total Accrual at December 31, 2013 $ 1,507 $ — $ — $ — $ 1,507 Charges 136 3,852 6,322 — 10,310 Payments (1,391 ) (3,515 ) (4,382 ) — (9,288 ) Non-cash items (6 ) — — — (6 ) Accrual at December 31, 2014 246 337 1,940 — 2,523 Credits — (322 ) (195 ) — (517 ) Payments (140 ) (15 ) (1,304 ) — (1,459 ) Non-cash items (106 ) — — — (106 ) Accrual at December 31, 2015 — — 441 — 441 (Credits) charges — — (319 ) 189 (130 ) Payments — — 317 — 317 Non-cash items — — (133 ) — (133 ) Accrual at December 31, 2016 $ — $ — $ 306 $ 189 $ 495 As of December 31, 2016 , the remaining accrual related to the Company's restructuring activities totaled $0.5 million and was included within the Accrued expenses and other line item in its consolidated balance sheets. The remaining accrual for the 2014 Corporate Restructuring primarily relates to lease termination costs, which are anticipated to be fully paid by the third quarter of 2020 .

Concentrations

Concentrations	12 Months Ended
	Dec. 31, 2016
Risks and Uncertainties [Abstract]
Concentrations	Concentrations Credit Risk Financial instruments that subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents, investments in marketable securities, and trade accounts receivable. The Company maintains its cash and cash equivalents with financial institutions that management deems reputable, and at times, cash balances may be in excess of FDIC insurance limits. The Company extends differing levels of credit to customers, typically does not require collateral, and maintains reserves for potential credit losses based upon the expected collectability of accounts receivable. Revenue by Product Line The Company has two product lines: Network Test Solutions ("NTS") and Network Visibility Solutions ("NVS"). NTS products include the Company's multi-slot test chassis and appliances, its traffic generation interface cards, its suite of test applications, and the related technical support, warranty, and software maintenance services, including its Application and Threat Intelligence ("ATI") subscription service. The Company's NVS products include network packet brokers, bypass switches, virtual and physical taps, and the related technical support, warranty, and software maintenance services, including its ATI subscription service available on certain NVS products. The following table presents revenue by product line (in thousands): Year Ended December 31, 2016 2015 2014 Network Test Solutions $ 349,557 $ 386,614 $ 345,673 Network Visibility Solutions 135,288 130,323 118,785 Total $ 484,845 $ 516,937 $ 464,458 Significant Customers For the years ended December 31, 2016 , 2015 , and 2014 , no customer comprised more than 10% of total revenues. As of December 31, 2016 and 2015 , no one customer had a receivable balance totaling more than 10% of total accounts receivable. International Data For the years ended December 31, 2016 , 2015 , and 2014 , total international revenues as a percentage of total revenues based on customer location consisted of the following: Year Ended December 31, 2016 2015 2014 International revenues 43.6 % 38.5 % 40.8 % As of December 31, 2016 and 2015 , property and equipment, net were geographically located as follows (in thousands): As of December 31, 2016 2015 United States $ 22,974 $ 23,654 Romania 6,482 6,542 India 3,385 3,576 Other 3,825 2,764 Total $ 36,666 $ 36,536

Selected Balance Sheet Data

Selected Balance Sheet Data	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Selected Balance Sheet Data	Selected Balance Sheet Data Allowance for Doubtful Accounts Activity in allowance for doubtful accounts during the years presented is as follows (in thousands): December 31, December 31, December 31, Balance at beginning of year $ 1,107 $ 1,011 $ 840 Additions: charged to costs and expenses 416 525 275 Deductions: write-offs, net of recoveries (612 ) (429 ) (104 ) Balance at end of year $ 911 $ 1,107 $ 1,011 Investments in Marketable Securities Investments in marketable securities as of December 31, 2016 consisted of the following (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Available-for-sale – short-term: U.S. Treasury, government, and agency debt securities $ 37,002 $ 24 $ (21 ) $ 37,005 Corporate debt securities 34,292 8 (54 ) 34,246 Total $ 71,294 $ 32 $ (75 ) $ 71,251 Investments in marketable securities as of December 31, 2015 consisted of the following (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Available-for-sale – short-term: U.S. Treasury, government, and agency debt securities $ 4,301 $ — $ (13 ) $ 4,288 Corporate debt securities 10,265 — (49 ) 10,216 Total $ 14,566 $ — $ (62 ) $ 14,504 As of December 31, 2016 and 2015 , unrealized losses on the Company's investments in available-for-sale securities that have been in a continuous unrealized loss position for more the 12 months or longer were insignificant. Unrealized losses related to these investments are due to interest rate fluctuations as opposed to changes in credit quality. In addition, the Company does not intend to sell, and it is not more likely than not that it would be required to sell, these investments before recovery of their amortized cost basis, which may be at maturity. As a result, there is no other-than-temporary impairment for these investments at December 31, 2016 . The amortized cost and fair value of our investments at December 31, 2016 , by contractual years-to-maturity, are as follows (in thousands): Amortized Cost Fair Value Due in less than 1 year $ 34,715 $ 34,706 Due within 1-2 years 20,928 20,928 Due within 2-5 years 10,051 10,017 Due after 5 years 5,600 5,600 Total $ 71,294 $ 71,251 Inventories Inventories consisted of the following (in thousands): December 31, December 31, Raw materials $ 1,252 $ 3,864 Work in process 6,581 11,253 Finished goods 20,824 18,172 Total $ 28,657 $ 33,289 Property and Equipment, Net Property and equipment, net consisted of the following (dollars in thousands): December 31, December 31, Useful Life (in years) Development equipment 5 $ 39,312 $ 35,831 Demonstration equipment 2 32,543 29,258 Furniture and other equipment 5 23,497 22,066 Computer software 3 - 5 22,803 20,702 Building and leasehold improvements 1 - 40 22,574 20,921 Computer equipment 3 17,929 16,698 Total 158,658 145,476 Accumulated depreciation (121,992 ) (108,940 ) Total $ 36,666 $ 36,536 Accrued Expenses and Other Accrued expenses and other consisted of the following (in thousands): December 31, December 31, Compensation and related expenses $ 12,428 $ 12,805 Vacation 5,724 7,967 Commissions 4,711 5,083 Professional fees 3,409 2,163 Other taxes 2,651 3,106 Bonuses 2,202 20,423 Legal contingencies 750 4,825 Income taxes 707 3,599 Other 6,820 10,058 Total $ 39,402 $ 70,029

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in the principal or most advantageous market for an asset or liability in an orderly transaction between market participants at the measurement date. The hierarchy below lists three levels of fair value based on the extent to which inputs used in measuring fair value are observable in the market. The Company categorizes each of its fair value measurements in one of these three levels based on the lowest level input that is significant to the fair value measurement in its entirety. This hierarchy prioritizes the inputs into three broad levels as follows: Level 1. Observable inputs such as quoted prices in active markets; 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. Financial assets carried at fair value as of December 31, 2016 and 2015 are summarized below (in thousands): December 31, 2016 December 31, 2015 Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents: Money market funds $ 769 $ 769 $ — $ — $ 284 $ 284 $ — $ — Corporate debt securities 7,943 — 7,943 — — — — — Marketable securities: U.S. Treasury, government and agency debt securities 37,005 — 37,005 — 4,288 — 4,288 — Corporate debt securities 34,246 — 34,246 — 10,216 — 10,216 — Total financial assets $ 79,963 $ 769 $ 79,194 $ — $ 14,788 $ 284 $ 14,504 $ — The Company's cash and investment instruments are classified within Level 1 or Level 2 of the fair value hierarchy based on quoted prices, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency. The fair values of the Company's money market funds, U.S. treasury, government and agency debt securities, and corporate debt securities are based on quoted market prices as shown in its investment brokerage/custodial statements. To the extent deemed necessary, the Company may also obtain non-binding dealer quotes to corroborate the estimated fair values reflected in its investment brokerage/custodial statements. There were no transfers of assets between levels within the fair value hierarchy for the years ended December 31, 2016 and 2015 , and there were no Level 3 assets held as of December 31, 2016 and 2015 . The carrying value of the Company's Term Loan at December 31, 2016 and 2015 was $35.0 million and $38.5 million , respectively. The carrying value of the Term Loan approximates fair value as the interest rate is variable over the selected interest period and is similar to current rates at which we can borrow funds.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets There was no activity within goodwill during 2016 or 2015 . The Company has not had any historical goodwill impairment charges. The following table presents the Company's purchased intangible assets (in thousands) as of December 31, 2016 : Weighted Average Useful Life Gross Accumulated Amortization Net (in years) Other intangible assets: Technology 5.5 $ 185,665 $ (151,672 ) $ 33,993 Customer relationships 6.0 71,700 (59,659 ) 12,041 Service agreements 6.4 30,100 (17,968 ) 12,132 Trademark 5.1 11,300 (8,966 ) 2,334 Non-compete agreements 4.0 8,000 (7,142 ) 858 Other 4.7 6,866 (2,547 ) 4,319 Total $ 313,631 $ (247,954 ) $ 65,677 The following table presents the Company's purchased intangible assets (in thousands) as of December 31, 2015 : Weighted Average Useful Life Gross Accumulated Amortization Net (in years) Other intangible assets: Technology 5.5 $ 185,665 $ (129,509 ) $ 56,156 Customer relationships 6.0 71,700 (51,533 ) 20,167 Service agreements 6.4 30,100 (13,272 ) 16,828 Trademark 5.1 11,300 (7,000 ) 4,300 Non-compete agreements 4.0 8,000 (5,641 ) 2,359 Other 4.5 5,750 (1,900 ) 3,850 Total $ 312,515 $ (208,855 ) $ 103,660 The estimated future amortization expense of purchased intangible assets as of December 31, 2016 is as follows (in thousands): 2017 $ 31,930 2018 20,666 2019 7,434 2020 3,892 2021 700 Thereafter 1,055 Total $ 65,677

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The components of income before income taxes were (in thousands): Year Ended December 31, 2016 2015 2014 U.S. $ (13,895 ) $ (5,307 ) $ (53,850 ) Foreign 30,684 19,650 1,153 Total $ 16,789 $ 14,343 $ (52,697 ) Income tax expense (benefit) consisted of the following (in thousands): Year Ended December 31, 2016 2015 2014 Current: Federal $ 7,260 $ 10,150 $ (372 ) State 684 1,635 1,111 Foreign 5,560 4,273 2,538 Deferred: Federal 25,981 (5,145 ) (12,479 ) State 11,299 (1,044 ) (1,916 ) Foreign (84 ) (1,477 ) 13 Income tax expense (benefit) $ 50,700 $ 8,392 $ (11,105 ) The net effective income tax rate differed from the federal statutory income tax rate of 35% as follows (dollars in thousands): 2016 2015 2014 Federal statutory expense $ 5,876 $ 5,020 $ (18,445 ) State taxes, net of federal benefit 11,866 269 (805 ) Research and development credits (1,603 ) (1,177 ) (1,585 ) Domestic production deduction (236 ) (595 ) — Foreign branch losses (2 ) 90 (1,213 ) Stock-based compensation 1,507 1,740 1,700 Foreign rate differential (5,463 ) (3,240 ) 1,633 Inter-company royalty 2,964 3,121 3,168 Inter-company transfer 1,994 1,994 1,841 Valuation allowance 31,077 (1,939 ) — Unrecognized tax benefits 1,157 1,160 1,497 Other 1,563 1,949 1,104 Income tax expense (benefit) $ 50,700 $ 8,392 $ (11,105 ) Net effective income tax rate 302.0 % 58.5 % 21.1 % The primary components of temporary differences that gave rise to deferred taxes were as follows (in thousands): December 31, December 31, Deferred tax assets: Research and development credit carryforward $ 13,734 $ 13,544 Deferred revenue 6,272 3,611 Stock-based compensation 11,474 10,674 Inventory adjustments 6,651 8,862 Net operating loss carryforward 4,331 4,939 Realized loss on investments 1,069 3,421 Accrued liabilities and other 1,117 1,056 Depreciation and amortization 5,894 958 Allowance for doubtful accounts 228 282 50,770 47,347 Valuation allowance (45,000 ) (2,056 ) 5,770 45,291 Deferred tax liabilities: Depreciation and amortization (202 ) (382 ) Intercompany royalty (10,537 ) (11,852 ) Net deferred tax (liabilities) assets $ (4,969 ) $ 33,057 As of December 31, 2016 and 2015 , long-term deferred tax assets totaled $1.3 million and $18.9 million , respectively, and were included as part of the Other Assets line item in the Company's consolidated balance sheets. As of December 31, 2015 , current deferred tax assets totaled $14.5 million and were included within the Prepaid Expenses and Other Current Assets line item in the Company's consolidated balance sheets. As of December 31, 2016 , the Company did not classify any of its deferred tax assets as current as a result of the Company's adoption of ASU 2015-17, which was adopted on a prospective basis. As of December 31, 2016 and 2015 , long-term deferred tax liabilities totaled $6.2 million and $0.4 million , respectively and were included within the Other Liabilities line item in the Company's consolidated balance sheets. The realizability of deferred income tax assets is based on a more likely than not standard. If it is determined that it is more likely than not that deferred income tax assets may not be realized, a valuation allowance must be established against the deferred income tax assets. As of December 31, 2016 , the Company had a valuation allowance of $44.0 million against its net deferred tax assets in the U.S. and $1.0 million against its Australian net operating loss carryforwards. For the years ended December 31, 2016 , 2015 , and 2014 , the Company recorded changes in its valuation allowance of $42.9 million , $2.3 million , and $214,000 , respectively. Prior to the fourth quarter of 2016, we maintained a valuation allowance against our net U.S. deferred tax assets of $1.1 million related to our realized capital loss carryforwards. In the fourth quarter of 2016, we evaluated the need for a valuation allowance against our remaining net deferred tax assets in the U.S. and concluded that a full valuation allowance was warranted due to the realization of a three-year cumulative pre-tax book loss in the U.S. As of December 31, 2016 , the Company has gross federal and state research and development credit carryforwards of $20.2 million and $19.4 million , respectively. The federal carryovers begin to expire in 2024 , while the state carryovers have an indefinite carryover period. As of December 31, 2016 , the Company has gross federal and state net operating loss (“NOLs”) carryforwards of $9.9 million and $2.0 million , respectively. The federal NOLs expire beginning 2028 , and the state NOLs begin to expire in 2018. Section 382 of the Internal Revenue Code imposes an annual limitation on the utilization of net operating loss carryforwards related to acquired corporations based on a statutory rate of return (usually the “applicable federal funds rate” as defined in the Internal Revenue Code) and the value of the corporation at the time of a “change in ownership” as defined by Section 382. The Company estimates that its 2016 limitation under Section 382 of the Internal Revenue Code is $0.7 million . Cumulative undistributed earnings of foreign subsidiaries for which no deferred income taxes have been provided were $124.4 million and $100.5 million at December 31, 2016 and 2015 , respectively. No provision for U.S. income and foreign withholding taxes has been made for unrepatriated foreign earnings because it is expected that such earnings will be reinvested indefinitely outside of the U.S. Under current tax laws and regulations, if our cash, cash equivalents, or investments associated with the subsidiaries’ undistributed earnings were distributed to the United States in the form of dividends or otherwise, it would be included in our U.S. taxable income, and we would be subject to additional U.S. income taxes and foreign withholding taxes. Determination of the amount of unrecognized deferred income tax liability related to these earnings is not practicable. At December 31, 2016 , the Company had gross unrecognized tax benefits of $23.5 million . Of this total, $6.6 million (net of the federal benefit on state issues) would affect its effective tax rate if recognized. The Company classifies liabilities for unrecognized tax benefits for which it does not anticipate payment or receipt of cash within one year in noncurrent other liabilities. The Company recognizes interest and penalties related to uncertain tax positions in income tax expense. During the years ended December 31, 2016 , 2015 and 2014 , the Company recognized $0 , $2,000 and $13,000 , net of federal benefit, of interest within our statements of operations. The Company had accrued interest, net of federal benefit, of $182,000 as of December 31, 2016 and 2015 . The Company files income tax returns in the U.S. federal jurisdiction and in various state and foreign jurisdictions. With few minor exceptions, the Company is no longer subject to U.S. federal, state and local, or non-U.S. income tax examinations by tax authorities in material jurisdictions for the tax years ended prior to 2009 . The U.S. Internal Revenue Service is currently examining the Company's 2009 through 2012 and 2014 federal income tax returns. The Company is subject to income tax in many jurisdictions both inside and outside of the U.S. The Company's operations in certain jurisdictions remain subject to examination, some of which are currently under audit by local tax authorities. The resolutions of these audits are not expected to be material to the Company's financial statements. A reconciliation of the beginning and ending amounts of gross unrecognized tax benefits is as follows (in thousands): 2016 2015 2014 Unrecognized tax benefits - beginning balance $ 21,178 $ 19,134 $ 16,766 Gross increases – tax positions taken in prior period 50 188 417 Gross decreases – tax positions taken in prior period (51 ) (161 ) (74 ) Gross increases – tax positions taken in current period 2,515 2,017 2,167 Lapse of statute of limitations (166 ) — (142 ) Unrecognized tax benefits – ending balance $ 23,526 $ 21,178 $ 19,134 The Company does not expect that its uncertain tax benefits will significantly increase or decrease in the next twelve months, unless the Company were to finalize its Advance Pricing Agreement ("APA"), as discussed below, with the IRS. On September 26, 2016, the Company was notified by the IRS of its proposal on the Company’s APA filed on January 15, 2013. Management responded to the IRS in the fourth quarter of 2016 and received an updated proposal from the IRS in the first quarter of 2017. Management is currently assessing the IRS's revised proposal. If the Company were to accept the proposal, it would be subject to the IRS's final review and approval. Management believes that it has sufficient reserves to offset any additional assessments as result of the proposed APA.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies The Company leases its facilities under non-cancelable operating leases for varying periods through May 2023 , excluding options to renew. Certain leases require the Company to pay property taxes, insurance, and routine maintenance, and include escalation clauses. The following are the future minimum commitments under these leases (in thousands): Year Ending December 31,* 2017 $ 11,849 2018 11,161 2019 9,496 2020 8,029 2021 5,290 Thereafter 8,282 Total $ 54,107 *Minimum payments have not been reduced by minimum sublease rentals of $43,000 due in the future under non-cancelable subleases. Rent expense for the years ended December 31, 2016 , 2015 , and 2014 was approximately $9.5 million , $8.9 million , and $13.7 million , respectively. 2016 Settlement of Securities Class Action On August 1, 2016 , the U.S. District Court for the Central District of California (the "Court") entered an order granting final approval of a Stipulation and Agreement of Settlement, dated November 11, 2015, providing for the settlement of the securities class action, captioned Oklahoma Firefighters Pension & Retirement System, et al. v. Ixia, et al ., filed in November 2013 against the Company and certain of our current and former officers and directors (the "Class Action Settlement Agreement"). The Class Action Settlement Agreement provides, among other terms, for a settlement payment in the amount of $3.5 million . In March 2016, one of our insurance carriers made the settlement payment, which will fund all payments to class members pursuant to the Class Action Settlement Agreement and the award of attorneys’ fees and expenses to plaintiffs’ counsel as approved by the Court. The settlement does not include any admission of wrongdoing or liability on the part of Ixia or the individual defendants and provides for a dismissal of, and a release of all claims asserted against the defendants in, the class action. By an amended order, dated February 21, 2017, the Court approved the distribution of the settlement fund to class members who had submitted claims. 2016 Settlement of Shareholder Derivative Action On June 1, 2016, the U.S. District Court for the Central District of California entered an order granting final approval of a Stipulation and Agreement of Settlement, dated November 17, 2015, providing for the settlement of the consolidated shareholder derivative action, captioned In re Ixia Shareholder Derivative Litigation , filed in May 2014 against Ixia, as a nominal defendant, and certain of its current and former officers and directors (the "Derivative Action Settlement Agreement"). The Derivative Action Settlement Agreement provides, among other terms, for Ixia to implement certain corporate governance measures. The court's final order also approved the award of attorneys’ fees and expenses to plaintiffs’ counsel in the amount of $575,000 , which has been paid by one of the Company's insurance carriers. The settlement does not include any admission of wrongdoing or liability on the part of Ixia or the individual defendants and provides for a dismissal of, and a release of all claims asserted against the defendants in, the derivative action. SEC Investigation On February 3, 2017, the Company reached a final settlement with the SEC that resolved matters related to the SEC’s investigation of its reporting, books and records, and internal controls in 2012 and the first two quarters of 2013. Under the terms of the settlement, Ixia, without admitting or denying the findings of the SEC, consented to the entry of an administrative order (the "Settlement Order") to cease and desist from future violations of the reporting, books and records, and internal controls provisions of the Securities Exchange Act of 1934, as amended, and certain rules adopted thereunder, and to pay a fine of $750,000 . The SEC noted in the Settlement Order that it had taken into consideration the Company's cooperation with the SEC's investigation as well as remedial actions undertaken by Ixia. The SEC did not allege fraud by Ixia. The payment of $750,000 was made to the SEC on February 9, 2017. The Company has accrued a liability of $750,000 related to this matter as a component of Accrued expenses and other in the accompanying consolidated balance sheets as of December 31, 2016 . Indemnifications In the normal course of business, the Company provides certain indemnifications, commitments, and guarantees of varying scope to customers, including against claims of intellectual property infringement made by third parties arising from the use of the Company's products. The Company also has certain obligations to indemnify its officers, directors, and employees for certain events or occurrences while the officers, directors, or employees are or were serving at the Company's request in such capacity. The duration of these indemnifications, commitments, and guarantees varies and in certain cases is indefinite. Many of these indemnifications, commitments, and guarantees do not provide for any limitation of the maximum potential future payments that the Company could be obligated to make. However, the Company's director and officer insurance policy may enable it to recover a portion of any future payments related to its officer, director, or employee indemnifications. Historically, costs related to these indemnifications, commitments, and guarantees have not been significant. With the exception of the product warranty accrual associated with the Company's initial standard warranty, no liabilities have been recorded for these indemnifications, commitments, and guarantees.

Shareholders_ Equity

Shareholders’ Equity	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Shareholders’ Equity	Shareholders’ Equity Stock Award Plans Second Amended and Restated Ixia 2008 Equity Incentive Plan The Company's Second Amended and Restated Ixia 2008 Equity Incentive Plan (the “2008 Plan” or the “Plan”), provides for the issuance of share-based awards to its eligible employees, directors, and consultants. The share-based awards may include incentive stock options ("ISO"), non-statutory stock options, stock appreciation rights, restricted stock units ("RSU"), or restricted stock awards. Options become exercisable over a vesting period as determined by the Board of Directors and expire over terms not exceeding 7 years from the date of grant. The exercise price for options granted under the 2008 Plan may not be granted at less than 100% of the fair market value of our common stock on the date of grant ( 110% for ISOs granted to an employee who owns more than 10% of the voting shares of the outstanding stock). Options generally vest over a four -year period. In the event the holder ceases to be employed by us, all unvested options are forfeited and all vested options may be exercised within a period of up to 90 days after termination other than (i) for termination for cause for which the vested options are forfeited on the termination date or (ii) as a result of death or disability for which vested options may be exercised for up to 180 days after termination. The 2008 Plan will terminate in May 2018, unless terminated sooner by the Board of Directors. In June 2013 , our shareholders approved the Second Amended and Restated Ixia 2008 Equity Incentive Plan, which resulted in amendments to the Company's Amended and Restated Ixia 2008 Equity Incentive Plan, as amended, which included the following: • Increase in Share Reserve. Increased the total number of shares of the Company's common stock available for future grants by 9.8 million shares for a total of 29.0 million shares of our common stock authorized and reserved over the term of the Plan, of which 6.1 million shares were available for future grant as of December 31, 2016 . • Types of Awards. Added cash awards to the types of awards that may be granted under the Plan, including performance-based incentives that are intended to comply with Section 162(m) of the Internal Revenue Code of 1986, as amended (the “Code”). • Award Limits. Added (i) a limit on the total number of shares (i.e., 1,000,000 ) subject to options and share appreciation rights granted to an eligible participant in any calendar year, (ii) with respect to performance-based awards that are intended to comply with the exception under Section 162(m) of the Code, limits on the total number of shares (i.e., 1,000,000 ) subject to RSUs and restricted stock awards that an individual may earn over a 12 -month period and on the total dollar amount (i.e., $2,000,000 ) subject to cash awards that an individual may earn over a 12 -month period, and (iii) a limit (i.e., $500,000 ) on the total dollar value of equity and cash awards that may be granted to a non-employee director in any calendar year. The 2008 Plan also provides for the following: • Shares Not Available for Awards. None of the following will be added to the shares available for awards under the Plan: (i) shares tendered by a participant or withheld by us in payment of the exercise price of an option, or to satisfy any tax withholding obligation with respect to options, and (ii) shares reacquired by the Company on the open market using cash proceeds from the exercise of options. • Acquisitions and Combinations. In connection with acquisitions and combinations by the Company, it may grant under the Plan awards in substitution or exchange for awards or rights to future awards previously granted by the acquired or combined company without reducing the shares available under the Plan. Any shares subject to but not issued under any such substitute awards would not become available for other awards granted under the Plan. Also, in the event that a company acquired by the Company or with which the Company combined has a pre-existing plan approved by its shareholders that was not adopted in contemplation of the acquisition or combination, available shares under that plan may be used for Plan awards without reducing the shares available under the Plan. Any such awards may only be made to persons who were not eligible to receive awards under the Plan prior to the acquisition or combination and may not be made after the date that awards could have been made under the terms of the pre-existing plan. The following table summarizes stock option activity for the year ended December 31, 2016 (in thousands, except per share and contractual life data): Number of Options Weighted Average Exercise Price Per Share Weighted Average Remaining Contractual Life (in years) Aggregate Intrinsic Value Outstanding as of December 31, 2015 5,474 $ 12.11 4.35 $ 9,350 Granted 1,240 11.30 Exercised (775 ) 8.68 Forfeited/canceled (459 ) 14.56 Outstanding as of December 31, 2016 5,480 $ 12.21 4.34 $ 22,638 Vested and expected to vest as of December 31, 2016 5,336 $ 12.23 4.30 $ 21,933 Exercisable at December 31, 2016 3,395 $ 12.96 3.56 $ 11,950 The weighted average grant-date fair value of options granted for the years ended December 31, 2016 , 2015 , and 2014 was $3.44 , $4.21 , and $3.36 per share, respectively. The total intrinsic value of options exercised during the years ended December 31, 2016 , 2015 , and 2014 was $3.1 million , $2.3 million , and $1.1 million , respectively. As of December 31, 2016 , the remaining unrecognized compensation expense related to stock options is expected to be recognized over a weighted average period of 1.38 years. The following table summarizes RSU activity for the year ended December 31, 2016 (in thousands, except per share data): Number of Awards Weighted Average Grant Date Fair Value Per Share Outstanding as of December 31, 2015 1,963 $ 12.63 Awarded 1,114 11.70 Vested (730 ) 13.10 Forfeited/canceled (188 ) 12.13 Outstanding as of December 31, 2016 2,159 $ 12.03 The fair value of RSUs vested during the years ended December 31, 2016 , 2015 , and 2014 was $8.0 million , $9.1 million , and $7.4 million , respectively. The weighted average remaining contractual life and expense recognition period of the outstanding RSUs as of December 31, 2016 was 1.41 years. Employee Stock Purchase Plan During 2010, the Company's shareholders approved the 2010 Employee Stock Purchase Plan (as amended, the “Purchase Plan”). The Purchase Plan permits eligible employees to purchase our common stock, subject to limitations as set forth in the Purchase Plan, through payroll deductions which may not exceed the lesser of 20% of an employee’s compensation or $21,250 per annum. The Purchase Plan is implemented in a series of consecutive, overlapping 24 -month offering periods, with each offering period consisting of four six -month purchase periods. Offering periods begin on the first trading day on or after May 1 and November 1 of each year. During each 24 -month offering period under the Purchase Plan, participants accumulate payroll deductions which, on the last trading day of each six-month purchase period within the offering period, are applied toward the purchase of shares of our common stock at a purchase price equal to 85% of the lower of (i) the fair market value of a share of the Company's common stock as of the first trading day of the 24 -month offering period and (ii) the fair market value of a share of the Company's common stock on the last trading day of the six-month purchase period. The Purchase Plan provides the potential for an automatic annual increase of up to 500,000 in the number of shares reserved for issuance under the Purchase Plan on May 1 of each year during the ten -year term of the plan. The Purchase Plan will terminate in March 2020 , unless it is earlier terminated by the Board of Directors. The Company also adopted a tax advantaged sub-plan under the Purchase Plan for its Romanian employees. Shares are issued under the Romania sub-plan from the authorized shares under the Purchase Plan. In June 2016, October 2015, and November 2014, the number of shares authorized and reserved for issuance under the Purchase Plan was increased by an additional 500,000 shares, respectively, pursuant to the automatic annual increase provision of the Purchase Plan. We have reserved a total of 5,300,000 shares of common stock for issuance under the Purchase Plan, of which 965,000 shares are available for future issuance for the existing and future offering periods. For the years ended December 31, 2016 , 2015 , and 2014 , approximately 1,026,000 , 988,000 , and 685,000 shares, respectively, were issued under the Purchase Plan. Stock-Based Compensation Expense The Black-Scholes option-pricing model is used to calculate the estimated fair value of share-based awards for options and RSUs on the respective dates of grant for accounting purposes using the following weighted average assumptions: Year Ended December 31, 2016 2015 2014 Expected lives (in years) 4.0 3.9 4.0 Risk-free interest rates 1.1 % 1.2 % 1.2 % Dividend yield — % — % — % Expected volatility 37.4 % 43.3 % 46.7 % The Black-Scholes option-pricing model is used to calculate the estimated fair value of share-based awards for our Purchase Plan for accounting purposes using the following weighted average assumptions: Year Ended December 31, 2016 2015 2014 Expected lives (in years) 1.3 1.3 1.2 Risk-free interest rates 0.6 % 0.4 % 0.2 % Dividend yield — % — % — % Expected volatility 35.7 % 28.4 % 32.9 % Expected lives (in years) - The expected life was determined by estimating the expected option life using historical data. Risk-free interest rates - The risk-free interest rate for periods equal to the expected term of the option is based on the U.S. Treasury yield curve in effect at the time of grant. Dividend yield - We have never declared or paid cash dividends on our common stock and do not anticipate paying any dividends in the foreseeable future. Volatility - The stock volatility is determined based on the weighted average historical weekly price changes of our common stock over the expected option term. Our stock-based compensation by award type is as follows (in thousands): Year Ended December 31, 2016 2015 2014 Options $ 4,438 $ 5,032 $ 3,934 RSUs 11,267 10,078 9,328 Common shares issued under the Purchase Plan 3,002 3,866 3,257 Total stock-based compensation $ 18,707 $ 18,976 $ 16,519 The aggregate balance of gross unrecognized stock-based compensation to be expensed in the years 2017 through 2021 related to unvested options, RSUs, and common shares issued under the Purchase Plan as of December 31, 2016 was $3.9 million , $11.8 million , and $4.0 million , respectively. There was no capitalized stock-based compensation for any of the periods presented. Accumulated Other Comprehensive Loss The following table summarizes, as of each balance sheet date, the changes in the Company's accumulated other comprehensive loss, by component, net of income taxes (in thousands): Unrealized Gains and Losses on Available-for- Sale Securities (a) Foreign Currency Items (a) Total Beginning balance, December 31, 2014 $ (32 ) $ (761 ) $ (793 ) Other comprehensive loss before reclassifications (76 ) (184 ) (260 ) Amounts reclassified from accumulated other comprehensive loss (b) 20 — 20 Net current-period other comprehensive loss (56 ) (184 ) (240 ) Ending balance, December 31, 2015 $ (88 ) $ (945 ) $ (1,033 ) Other comprehensive gain before reclassifications 75 63 138 Amounts reclassified from accumulated other comprehensive loss (b) (13 ) — (13 ) Net current-period other comprehensive gain 62 63 125 Ending balance, December 31, 2016 $ (26 ) $ (882 ) $ (908 ) (a) All amounts are net-of-tax. Amounts in parentheses indicate reductions. (b) Amount represents gain on the sale of securities and is included as a component of Interest income and other, net in the consolidated statements of operations. Other Comprehensive Income (Loss) The Company sold available-for-sale securities in the years ended December 31, 2016 and 2015 which resulted in a reclassification from accumulated other comprehensive loss of realized gains totaling $13,000 and realized losses totaling $20,000 , respectively, which were included within the Interest income and other, net line item in the Company's consolidated statements of operations. Prior to the reclassification of realized gains and losses related to the sale of available-for-sale securities, the Company had gross unrealized gains of $118,000 for the year ended December 31, 2016 and gross unrealized losses of $125,000 for the year ended 2015 . Stock Buyback Program On February 23, 2016 , the Company’s Board of Directors approved a share repurchase program (the "Program") authorizing the Company, over the 12 months following the announcement, to acquire up to $25 million of its common stock. Under the Program, the Company was authorized, from time to time, and subject to general business and market conditions, alternative investment opportunities, and other factors, to repurchase shares in open market purchases, privately negotiated transactions, and/or through other means, and may include repurchases pursuant to a Rule 10b5-1 trading plan. The Program expired on February 22, 2017. There is no guarantee as to the exact number of shares that will be repurchased by the Company, and the Company may discontinue or suspend repurchases at any time in the Company’s discretion. During the year ended December 31, 2016 , the Company repurchased 707,332 shares of its common stock for approximately $6.9 million . All of the repurchased shares remain authorized, but are no longer issued and outstanding. As of December 31, 2016 , $18.1 million remained available for share repurchases under the Program.

Retirement Plan

Retirement Plan	12 Months Ended
	Dec. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Retirement Plan	Retirement Plan The Company provides a 401(k) Retirement Plan (the “Plan”) to eligible employees who may authorize contributions up to IRS annual deferral limits to be invested in employee elected investment funds. As determined annually by the Board of Directors, the Company may contribute matching funds of 50% of the employee contributions up to $2,500 . These matching contributions vest based on the employee’s years of service with the Company. For the years ended December 31, 2016 , 2015 , and 2014 , the Company expensed and made contributions to the Plan in the amount of $2.9 million , $3.0 million , and $1.6 million , respectively.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share The following table sets forth the computation of basic and diluted earnings (loss) per share for the periods indicated (in thousands, except per share data): Year Ended December 31, 2016 2015 2014 Basic Presentation: Numerator for basic (loss) earnings per share: Net (loss) income $ (33,911 ) $ 5,951 $ (41,592 ) Denominator for basic (loss) earnings per share: Weighted average common shares outstanding 81,470 79,633 77,629 Basic (loss) earnings per share $ (0.42 ) $ 0.07 $ (0.54 ) Diluted presentation: Numerator for diluted (loss) earnings per share: Net (loss) income $ (33,911 ) $ 5,951 $ (41,592 ) Denominator for diluted (loss) earnings per share: Weighted average common shares outstanding 81,470 79,633 77,629 Effect of dilutive securities: Stock options and other share-based awards — 1,826 — Dilutive potential common shares 81,470 81,459 77,629 Diluted (loss) earnings per share $ (0.42 ) $ 0.07 $ (0.54 ) The diluted loss per share computation for the year ended December 31, 2016 excluded the weighted average number of shares underlying the Company's employee stock options and other share-based awards of 4.7 million shares, which were anti-dilutive because the Company reported a net loss for the year ended December 31, 2016 . The diluted income per share computation for the year ended December 31, 2015 , excluded (i) the weighted average number of shares underlying the Company's then-outstanding convertible senior notes of 8.4 million shares as they are considered anti-dilutive because the related interest expense on a per common share “if converted” basis exceeded basic earnings per share, and (ii) the weighted average number of shares underlying the employee stock options and other share-based awards of 2.6 million shares, which were anti-dilutive because, the exercise prices of these awards exceeded the average closing sales price per share of the Company's common stock during the applicable period. The diluted loss per share computation for the year ended December 31, 2014 , excluded (i) the weighted average number of shares underlying the then outstanding convertible senior notes of 10.3 million shares as they are considered anti-dilutive because the related interest expense on a per common share “if converted” basis exceeded the basic loss per share, and (ii) the weighted average number of shares underlying the employee stock options and other share-based awards of 4.7 million shares, which were anti-dilutive because the Company reported a net loss for the year ended December 31, 2014 .

Quarterly Financial Summary (Un

Quarterly Financial Summary (Unaudited)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Summary (Unaudited)	Quarterly Financial Summary (Unaudited) For the three months ended 2016 2015 Dec. 31 Sep. 30 Jun. 30 Mar. 31 Dec. 31 Sep. 30 Jun. 30 Mar. 31 (in thousands) Consolidated Statement of Operations Data: Total revenues $ 128,163 $ 123,911 $ 120,098 $ 112,673 $ 138,478 $ 125,887 $ 131,610 $ 120,962 Total cost of revenues (1) 33,558 33,352 30,343 31,660 35,697 33,913 34,983 35,001 Gross profit 94,605 90,559 89,755 81,013 102,781 91,974 96,627 85,961 Income (loss) before income taxes 6,949 6,560 8,249 (4,969 ) 12,309 506 6,574 (5,046 ) Net (loss) income (2) (37,520 ) 4,773 1,523 (2,687 ) 5,751 4,008 5,803 (9,611 ) (Loss) earnings per share: Basic $ (0.46 ) $ 0.06 $ 0.02 $ (0.03 ) $ 0.07 $ 0.05 $ 0.07 $ (0.12 ) Diluted $ (0.46 ) $ 0.06 $ 0.02 $ (0.03 ) $ 0.07 $ 0.05 $ 0.07 $ (0.12 ) (1) For the quarters ended: December 31, 2016 ; September 30, 2016 ; June 30, 2016 ; March 31, 2016 ; December 31, 2015 ; September 30, 2015 ; June 30, 2015 ; and March 31, 2015 ; total cost of revenues includes charges related to amortization of intangible assets of $6.2 million , $6.3 million , $6.4 million , $6.4 million , $6.4 million , $6.4 million , $6.4 million , and $6.4 million , respectively. (2) In the quarter ended December 31, 2016 , income tax expense includes a $42.9 million charge related to the establishment of a valuation allowance against the Company's remaining net deferred tax assets in the U.S.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2016
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Pending Acquisition by Keysight The Company entered into an Agreement and Plan of Merger, dated as of January 30, 2017 (the "Merger Agreement"), with Keysight Technologies, Inc. (“Keysight”) and, by a joinder dated February 2, 2017, Keysight Acquisition, Inc., a wholly owned subsidiary of Keysight (“Merger Sub”). Pursuant to the Merger Agreement, subject to the approval of the Merger Agreement and the principal terms of the Merger Agreement by the Company's shareholders and the satisfaction of other conditions to the completion of the merger specified in the Merger Agreement, Merger Sub will be merged with and into Ixia (the "Merger"), with Ixia surviving the merger as a wholly owned subsidiary of Keysight. Subject to certain exceptions, at the effective time of the Merger, each share of the Company's common stock issued and outstanding immediately prior to the effective time will be converted into the right to receive $19.65 in cash, without interest (“Per Share Merger Consideration”), subject to any applicable tax withholding. Options, whether vested or unvested, to acquire the Company's common stock that are outstanding immediately prior to the consummation of the Merger will, at the effective time, become fully vested (to the extent not then vested) and be canceled in exchange for the right to receive an amount in cash equal to the excess, if any, of the Per Share Merger Consideration over the exercise price per share of the options, subject to any applicable tax withholding. Each restricted stock unit covering shares of the Company's common stock that is outstanding immediately prior to the Merger will, at the effective time, be canceled in exchange for the right to receive an amount in cash equal to the Per Share Merger Consideration (with any restricted stock units subject to performance-based vesting conditions to be earned at target performance levels), subject to any applicable tax withholdings. Consummation of the Merger is subject to customary closing conditions, including, without limitation, (i) the approval of the Merger Agreement and the principal terms thereof by the Company's shareholders, (ii) the expiration or termination of any waiting period (and any extension thereof) under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, and (iii) the receipt of necessary approvals from certain foreign antitrust authorities. Consummation of the Merger is not subject to a financing condition. The Company has made customary representations and warranties and has agreed to specified covenants in the Merger Agreement, including covenants relating to the conduct of the Company’s business between the date of the Merger Agreement and the consummation of the Merger (or if earlier, the termination of the Merger Agreement). The Merger Agreement contains certain termination rights of Keysight and the Company and provides that the Company will be required to pay Keysight a termination fee of approximately $59.7 million upon termination of the Merger Agreement under certain circumstances, including, but not limited to, if the Company accepts a superior acquisition proposal. In addition, if the Company terminates the Merger Agreement for Keysight’s failure to close when required to do so pursuant to the Merger Agreement, Keysight will be required to pay the Company a termination fee of $500 million . Either party may terminate the Merger Agreement if the Merger is not consummated by the “end date” of the Merger Agreement, which is 5:00 p.m. (Eastern Time) on October 30, 2017, subject to certain limitations. The Company incurred approximately $802,000 of costs related to the Merger in 2016 , primarily consisting of professional fees. These costs have been included within the Acquisition and other related costs line item on the Company's consolidated statements of operations. Litigation Relating to Pending Acquisition by Keysight On February 23, 2017, a purported shareholder of the Company filed a putative class action lawsuit, captioned Colleen Witmer v. Ixia, Errol Ginsberg, Bethany Mayer, Laurent Asscher, Jonathan Fram, Gail Hamilton, Ilan Daskal, Keysight Technologies, Inc., and Keysight Acquisition, Inc. , in the U.S. District Court for the Central District of California. The lawsuit, which purports to be a class action brought on behalf of the shareholders of the Company, challenges the proposed Merger and the Company's disclosures in connection with the Merger. The complaint alleges, among other things, that the Company omitted material information with respect to the proposed Merger in the preliminary proxy statement that the Company filed with the SEC on February 15, 2017 in connection with the proposed Merger and that, as a result, (i) the Company and the members of its Board of Directors violated Section 14(a) of the Exchange Act and Rule 14a-9 promulgated thereunder, and (ii) such directors, as well Keysight and Merger Sub, violated Section 20(a) of the Exchange Act. The complaint seeks relief that includes an order enjoining the proposed Merger or, if the Merger is consummated, rescinding the Merger or awarding rescissory damages; direction that the directors disseminate a revised proxy statement; and an award of the plaintiff's costs of the action, including reasonable attorneys' and experts' fees. The complaint has not been served on the Company. If the complaint is served on the Company, the Company intends to pursue its defenses vigorously.

Description of Business, Basi24

Description of Business, Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements (Policies)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements for the years ended December 31, 2016 , 2015 , and 2014 have been prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP").
Use of Estimates	Use of Estimates In the normal course of preparing financial statements in conformity with GAAP, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Principles of Consolidation	Principles of Consolidation All subsidiaries are consolidated as they are 100% owned by us. All intercompany transactions and accounts are eliminated in consolidation.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with a maturity of three months or less at the date of purchase to be cash equivalents. Cash is carried at cost, which approximates fair value, and cash equivalents are carried at fair value. The Company generally invests funds that are in excess of current needs in high credit quality instruments such as money market funds. There are no restrictions on the use of cash and cash equivalents.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company's financial instruments, including cash, accounts receivable, and accounts payable are carried at cost, which approximates their fair values because of the short-term maturity of these instruments and the relative stability of interest rates. The fair values of the Company's cash equivalents, money market funds, U.S. treasury, government and agency debt securities, and corporate debt securities are based on quoted market prices as shown in its investment brokerage/custodial statements. Fair value is defined as the exit price, or the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants as of the measurement date. There is an established hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring the most observable inputs be used when available. Observable inputs are inputs market participants would use in valuing the asset or liability and are developed based on market data obtained from independent sources. Unobservable inputs are inputs that reflect the assumptions about the factors that market participants would use in valuing the asset or liability.
Foreign Currency Forward Contracts	Foreign Currency Forward Contracts The Company utilizes foreign currency forward contracts to hedge certain accounts receivable amounts that are denominated in Japanese Yen, Euros, and British Pounds. These contracts are cash flow hedges used to reduce the risk associated with exchange rate movements, as gains and losses on these contracts are intended to offset exchange losses and gains on underlying exposures. Foreign currency contracts are typically short-term in duration ranging from one to four months. The Company does not enter into foreign exchange forward contracts for speculative or trading purposes. In accordance with ASC 815, “Derivatives and Hedging,” the Company records all derivatives in the consolidated balance sheet as either assets or liabilities measured at fair value. The Company’s foreign currency contracts are generally not designated as hedges and any gains or losses on the movement in their fair values is recognized in the results of operations immediately. Foreign currency contracts are recorded at fair market values as a component of Prepaid expenses and other current assets in the consolidated balance sheet and the change in their fair value is recorded as a gain or loss in the consolidated statements of operations as a component of Interest income and other, net .
Investments in Marketable Securities	Investments in Marketable Securities The Company maintains a portfolio of cash equivalents and investments in a variety of fixed and variable rate securities, including U.S. government and federal agency securities, corporate debt securities, and money market funds. The primary objective of the Company's investment activities is to maintain the safety of principal and preserve liquidity while maximizing yields without significantly increasing risk. The Company does not enter into investments for trading or speculative purposes. The Company determines the appropriate classification of investments in marketable securities at the time of purchase. Accretion and amortization of purchase discounts and premiums are included in Interest income and other, net . Available-for-sale securities are stated at fair value. The net unrealized gains or losses on available-for-sale securities are reported as a separate component of accumulated other comprehensive income or loss, net of tax. The specific identification method is used to compute realized gains and losses on marketable securities. In 2016 , 2015 , and 2014 , gross realized gains and losses were not significant. The Company regularly reviews its investment portfolio to determine if any security is other-than-temporarily impaired, which would require it to record an impairment charge in the period any such determination is made. In making this judgment, the Company evaluates, among other things, the duration and extent to which the fair value of a security is less than its cost, and its intent and ability to sell, or whether it will more likely than not be required to sell, the security before recovery of its amortized cost basis. The Company has evaluated its investments as of December 31, 2016 and has determined that no investments with unrealized losses are other-than-temporarily impaired. The Company does not intend to sell any investments whose fair value is currently below cost, and it is not more likely than not that it would be required to sell these investments, before recovery of the amortized cost basis, which may be at maturity. It is possible that the Company could recognize future impairment charges on the investment securities it currently owns if future events, new information, or the passage of time cause the Company to believe that a decline in the carrying value of its securities is other-than-temporary. The Company will continue to review and analyze these securities for triggering events each reporting period. See Note 6 for additional information.
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful Accounts Trade accounts receivable are recorded at the invoiced amount. The allowance for doubtful accounts is based on the Company's best estimate of the amount of probable credit losses in existing accounts receivable. The Company reviews the allowance for doubtful accounts, and provisions are made upon a specific review of all significant past due receivables. For those receivables not specifically reviewed, provisions are provided at a general rate that considers historical write-off experience and other qualitative factors. Account balances are charged off against the allowance when the Company believes it is probable the receivable will not be recovered.
Inventories	Inventories Inventories are goods held for sale in the normal course of business. Inventories are stated at the lower of cost (first-in, first-out) or market. The inventory balance consists of raw materials, work in process (“WIP”), and finished goods. Raw materials include low level components, many of which are purchased from vendors, WIP consists of partially assembled products, and finished goods are products that are ready to be shipped to end customers. Consideration is given to inventory shipped and received near the end of a period, and the transaction is recorded when transfer of title occurs. The Company evaluates inventory for excess and obsolescence and adjusts its carrying amount to net realizable value based on inventory that is obsolete or in excess of current demand.
Property, Plant and Equipment	Property, Plant, and Equipment Property, plant, and equipment are stated at cost less accumulated depreciation. Depreciation of the Company's computer software and equipment is computed using the straight-line method based upon the estimated useful lives of the applicable assets, ranging from three to five years. Building and leasehold improvements are amortized over the lesser of their estimated useful lives or the remaining lease term. Useful lives are evaluated periodically by management in order to determine recoverability in light of current technological conditions. Property, plant, and equipment also include the cost of the Company's products used for research and development which are classified as development equipment and are depreciated over five years to research and development. The Company also capitalizes and depreciates over a two -year period costs of its products used for sales and marketing activities, including product demonstrations for potential customers, which is included in Sales and marketing in the consolidated statements of operations. Repair and maintenance costs are charged to expense as incurred while renewals and improvements are capitalized. Upon the sale or retirement of property, plant, and equipment, the accounts are relieved of the cost and the related accumulated depreciation, with any resulting gain or loss included in the consolidated statements of operations.
Goodwill and Intangible Assets	Goodwill The Company records goodwill as the difference, if any, between the aggregate consideration paid for an acquisition and the fair value of the acquired net tangible and identifiable intangible assets. The Company evaluates the recoverability of its goodwill on an annual basis or if events or changes in circumstances indicate that impairment in the value of goodwill recorded on its balance sheet may exist. The Company has determined that it has one reporting unit for goodwill impairment testing purposes. The fair value of the Company’s reporting unit is determined using the market capitalization of Ixia, which considers the observed market price of the Company’s publicly-traded equity securities on the impairment test date. The fair value of the Company’s reporting unit is then compared to the carrying amount of the Company’s reporting unit under “step 1” of the impairment testing model. If the carrying value of the reporting unit exceeds its fair value, then the fair value of goodwill is determined and compared to its carrying value under “step 2.” Impairment losses are recorded to the extent that the carrying value of the goodwill exceeds its estimated fair value. The Company completed its annual goodwill impairment test of its single reporting unit as of December 31, 2016 and determined that there was no impairment. Intangible Assets Intangible assets consist primarily of acquired intellectual property and other long-lived assets, such as purchased technology, customer relationships, service agreements, trade names, and non-compete agreements. Acquired intangible assets with finite lives are amortized over their estimated useful lives and reflected in the Amortization of intangible assets line item on the consolidated statements of operations. Intangible assets with finite lives are tested for impairment whenever events or circumstances indicate that the carrying amount of an asset (asset group) may not be recoverable. Circumstances which could trigger a review include, but are not limited to: significant adverse change in the extent or manner in which the intangible asset is being used; significant adverse changes in the business climate or legal factors; current period cash flow or operating losses combined with a history of losses or a forecast of continuing losses associated with the use of the asset; or a current expectation that the asset will more likely than not be sold or disposed of significantly before the end of its estimated useful life. An impairment loss is recognized when the carrying amount of an asset exceeds the estimated undiscounted cash flows used in determining the fair value of the asset. The amount of the impairment loss recorded is calculated as the excess of the asset’s carrying value over its fair value. Fair value is generally determined using a discounted cash flow analysis and may involve the use of significant estimates and assumptions, some of which may be based in part on historical experience, forecasted information, and discount rates.
Litigation	Litigation The Company accrues for losses when the loss is deemed probable and the liability can reasonably be estimated. Where a liability is probable and there is a range of estimated loss with no best estimate in the range, the Company records the minimum estimated liability related to the claim. As additional information becomes available, the Company assesses the potential liability related to its pending litigation and revises its estimates. See Note 10 for additional information.
Product Warranty	Product Warranty The Company generally provides an initial standard warranty ( 90 -day or 12 -month periods) on its hardware products after product shipment and accrues for estimated future warranty costs based on actual historical experience and other relevant data, as appropriate, at the time product revenue is recognized. All product warranty expenses associated with the Company's initial standard warranty is reflected within Cost of revenues-products in the accompanying consolidated statements of operations. Accrued product warranty costs are included as a component of Accrued expenses and other in the accompanying consolidated balance sheets.
Revenue Recognition	Revenue Recognition Sales of the Company's network test hardware products primarily consist of traffic generation and analysis hardware platforms containing multi-slot chassis and interface cards. The Company's primary network test hardware platform is enabled by its operating system software that is essential to the functionality of the hardware platform. Sales of the Company's network visibility hardware products typically include an integrated, purpose-built hardware appliance with essential, proprietary software. The Company's software products consist of a comprehensive suite of technology-specific applications for certain of its network test hardware platforms. The Company's software products are typically installed on and work with these hardware products to further enhance the core functionality of the overall network test system, although some of its software products can be operated independently from its network test platforms. The Company's service revenues primarily consist of technical support, warranty, and software maintenance services related to its network test and visibility hardware and software products. Many of the Company's products include up to one year of these services with the initial product purchase, and its customers may separately purchase extended services for annual or multi-year periods. The Company's technical support, warranty, and software maintenance services include assistance with the set-up, configuration, and operation of its products, repair or replacement of defective products, bug fixes, and unspecified when and if available software upgrades. For certain network test products, the Company's technical support and software maintenance service revenues also include its Application and Threat Intelligence ("ATI") subscription service, which provides a comprehensive suite of application protocols, software updates, and technical support. The ATI subscription service provides full access to the latest security attacks and application updates for use in real-world test and assessment scenarios. The Company's customers may purchase the ATI subscription service for annual or multi-year periods. Service revenues also include training and other professional services. As the Company's systems typically include hardware and software products and the related services, the Company recognizes its revenue in accordance with authoritative guidance on both hardware and software revenue recognition. Furthermore, in accordance with the current revenue recognition guidance, the Company's hardware platform and certain other products that include both tangible products and software elements that function together to deliver the tangible product’s essential functionality have been scoped out of software revenue recognition guidance, and therefore these products are accounted for as hardware products for revenue recognition purposes. The Company recognized revenue for hardware and software products and related services based on the following four criteria: whether (i) evidence of an arrangement exists, which is typically in the form of a customer purchase order; (ii) delivery has occurred (i.e., risks and rewards of ownership have passed to the customer); (iii) the sales price is fixed or determinable; and (iv) collectability is deemed reasonably assured (or probable for software-related deliverables). Provided that the above criteria are met, revenue from hardware and software product sales is typically recognized upon shipment, and service revenues are recognized as the services are provided or completed. The Company recognizes service revenues from its initial and separately purchased technical support, warranty, and software maintenance arrangements on a straight-line basis over the applicable contractual period. The Company's systems are generally fully functional at the time of shipment and do not require the Company to perform any significant production, modification, customization, or installation after shipment. If an arrangement includes acceptance provisions based on customer specified criteria for which it cannot reliably demonstrate that the delivered product meets all the specified criteria, revenue is deferred until the earlier of the receipt of written customer acceptance or the expiration of the acceptance period. In addition, the arrangements generally do not include any provisions for cancellation, termination, or refunds.
Multiple Element Arrangements and Allocation of Value	Multiple Element Arrangements and Allocation of Value The Company's sales arrangements with its customers typically include a combination of its hardware and software products, as well as the related technical support, warranty, and software maintenance services of these products, and therefore are commonly referred to as multiple element arrangements. When sales arrangements involve hardware and software elements, the Company uses a two-step process to allocate value to each element in the arrangement: (1) The total arrangement fee is allocated to the separate non-software deliverables (e.g., chassis, interface cards, and software post contract customer support and maintenance (“PCS”) related to the Company's operating system software that is essential to the functionality of its hardware platform) and the software-related deliverables as a group (e.g., application software and software PCS) based on a relative selling price (“RSP”) method applied to all elements in the arrangement using the selling price hierarchy in the revenue recognition guidance as discussed below; and (2) The value assigned to the software group for the software deliverables is then allocated to each software element based on the residual method, whereby value is allocated first to the undelivered elements, typically PCS, and the residual portion of the value is then allocated to the delivered elements (typically the software products) and recognized as revenue, provided all other revenue recognition criteria discussed above have been met. The fair value of an element must be based on vendor specific objective evidence (“VSOE”) of the selling price, which typically only exists for technical support, warranty, and software maintenance services as discussed below. Under the RSP method, the selling price to be used in the allocation of the total arrangement fee to each of the elements, or deliverables, is based on a selling price hierarchy, where the selling price for each element is based on (i) VSOE, if available; (ii) third-party evidence (“TPE”), if available and VSOE is not available; or (iii) the best estimate of selling price (“BESP”), if neither VSOE nor TPE are available. The Company determines VSOE of fair value based on a bell-shaped curve approach, considering the actual sales prices charged to customers when the same element is sold separately, provided it is substantive. All of the Company's products are sold as multiple element arrangements and not sold separately, as its products include an initial period (generally 90 -day or 12 -month periods) of free technical support, warranty, and software maintenance services. Accordingly, the Company has not established VSOE for nearly all of its products. On a regular basis, the Company separately sells extended technical support, warranty, and software maintenance services upon the expiration of the initial contractual periods included in an initial sales arrangement and have been able to establish VSOE for its technical support, warranty, and software maintenance services. The Company generally is not able to determine TPE for its products or services because its products are not interchangeable with those of its competitors. Furthermore, the Company is unable to reliably determine competitive selling prices when the applicable competitive products are sold separately. As such, the Company uses BESP for all of its products and services when allocating the total consideration of multiple element arrangements to each of the deliverables under step one of the allocation process described above except for its technical support, warranty, and software maintenance services where it uses VSOE. The Company determines BESP for a product or service by considering multiple factors including, analyzing historical sales price data for stand-alone and bundled arrangements, published price lists, geographies, and customer types. The Company's estimate of BESP used in its allocation of arrangement consideration requires significant judgment, and the Company reviews these estimated selling prices on a quarterly basis. The allocation of value to each deliverable in a multiple element arrangement is completed at the inception of an arrangement, which is typically the receipt of a customer purchase order. The allocated value of each non-software deliverable is then recognized as revenue when each element is delivered, provided all of the other revenue recognition criteria discussed above have been met. For software deliverables, the total software group allocation (or total arrangement consideration for customer orders that include only software products and related services) is allocated based on the residual method which requires that the Company first allocates value to the undelivered element at VSOE of the selling price of the undelivered element and the remaining portion of the arrangement fee is allocated to the delivered elements. As the Company does not sell its software products without technical support, warranty, and software maintenance services, it is unable to establish VSOE for its software products, and therefore uses the residual method under the software revenue recognition guidance to allocate the software group (or arrangement) value to each software deliverable. Under the residual method, the software group (or arrangement) value is allocated first to the undelivered elements, typically technical support, warranty, and software maintenance services based on VSOE, and the residual portion of the value is then allocated to the delivered elements (typically the software products) and recognized as revenue, provided all other revenue recognition criteria discussed above have been met. If VSOE cannot be established for an undelivered element within the software group (or arrangement), the value allocated to the software group (or arrangement) is deferred until the earlier of (i) delivery of all elements (other than technical support, warranty, and software maintenance services) or (ii) establishment of VSOE of the undelivered element(s). If the only undelivered element(s) relates to a service for which VSOE has not been established, the entire allocated value of the software group (or arrangement) is recognized as revenue over the longer of the service or contractual period of the technical support, warranty, and software maintenance services. VSOE of fair value typically only exists for the Company’s technical support, warranty, and software maintenance services (“Support”). VSOE of fair value is established using the bell-shaped curve approach for a subgroup when a substantial majority (generally greater than 75% ) of the transactions are priced within a reasonably narrow range (generally plus or minus 15% from the list price, which approximates the median). On a regular basis, the Company separately sells Support upon the expiration of the initial contractual periods included in an initial sales arrangement (“Support Renewals”). The population of Support Renewals is used in the bell-shaped curve approach to establish VSOE of fair value of Support and consists of actual sales prices charged to customers for Support Renewals and includes only Support Renewals sold separately on a stand-alone basis. The Company reviews these stand-alone sales of its Support Renewals for VSOE of fair value of its Support on a quarterly basis (“VSOE Analysis”). The Company’s pricing for Support Renewal transactions is generally based on a percentage of the Company’s list price for the product for which the Support Renewal is being purchased. When pricing conditions vary significantly, the Company further stratifies the population of stand-alone sales of its Support Renewals based on Support Renewal pricing conditions and separately analyzes these subgroups of Support Renewal transactions. The Company’s Support Renewal pricing conditions consist of the underlying product type, product family, customer type, and the geographic region in which the sale is made.
Sales to Distributors	Sales to Distributors The Company uses distributors and resellers to complement its direct sales and marketing efforts in certain markets and/or for certain products. Due to the broad range of features and options available with the Company's hardware and software products, distributors and resellers generally do not stock the Company's products and typically place orders with the Company after receiving an order from an end customer. These distributors and resellers receive business terms of sale similar to those received by the Company's other customers; and payment to the Company is not contingent on sell-through to and receipt of payment from the end customer. As such, for sales to distributors and resellers, the Company recognizes revenue when the risks and rewards of ownership have transferred to the distributor or reseller provided that the other revenue recognition criteria noted above have been met.
Cost of Revenues	Cost of Revenues The Company's cost of revenues related to the sale of its hardware and software products includes materials, payments to third party contract manufacturers, royalties, and salaries and other expenses related to its manufacturing and supply operations personnel. The Company outsources the majority of its manufacturing operations. Accordingly, a significant portion of the Company's cost of revenues related to its products consists of payments to its contract manufacturers. Cost of revenues related to the provision of services includes salaries and other expenses associated with technical support services and the cost of extended warranty and maintenance services. Cost of revenues does not include the amortization of purchased technology related to the Company's acquisitions of certain businesses, product lines, and technologies
Shipping and Handling Costs	Shipping and Handling Costs Shipping and handling costs are reported in Sales and marketing expenses in the Company's consolidated statements of operations.
Research and Development	Research and Development Research and development expenses consist primarily of salaries and other personnel costs related to the design, development, testing, and enhancement of the Company's products. Costs related to research and development activities, including those incurred to establish the technological feasibility of a software product, are expensed as incurred. If technological feasibility is established, all development costs incurred until general product release are subject to capitalization. To date, establishment of technological feasibility of the Company's products and general release have substantially coincided. As a result, the Company has not capitalized any development costs.
Software Developed for Internal Use	Software Developed for Internal Use The Company capitalizes costs of software, consulting services, hardware, and payroll-related costs incurred to purchase or develop internal-use software in accordance with the authoritative guidance on accounting for the costs of computer software developed or obtained for internal use. Internally developed software includes enterprise-level business software that the Company is customizing to meet its specific operational needs. To date, internal costs incurred to purchase or develop software for internal use have not been significant. Internally developed software is amortized over five years.
Advertising	Advertising Advertising costs are expensed as incurred.
Acquisition and Other Related Costs	Acquisition and Other Related Costs Acquisition and other related costs are expensed as incurred and consist primarily of transaction and integration related costs such as success-based banking fees, professional fees for legal, accounting, tax, due diligence, valuation, and other related services, change in control payments, amortization of deferred compensation, consulting fees, required regulatory costs, certain employee, facility, and infrastructure transition costs, and other related expenses. The Company expects its acquisition and other related costs to fluctuate over time based on the timing of its acquisitions and related integration activities.
Stock-Based Compensation	Stock-Based Compensation Share-based payments, including grants of stock options, restricted stock units, and employee stock purchase rights, are required to be recognized in the financial statements based on the estimated fair values for accounting purposes on the grant date. The Company uses the Black-Scholes option pricing model to estimate the fair value for accounting purposes of stock options and employee stock purchase rights. The Company uses the grant date closing share sales price of a share of its common stock to estimate the fair value for accounting purposes of restricted stock units. The determination of the fair value of share-based awards utilizing the Black-Scholes model is affected by the Company's stock price and a number of assumptions, including expected volatility, expected life, and the risk-free interest rate. The expected life and expected volatility are estimated based on historical data. The risk-free interest rate assumption is based on U.S. Treasury constant maturity yields over the expected life of the award. Stock-based compensation expense recognized in the Company's consolidated financial statements is based on awards that are ultimately expected to vest. The amount of stock-based compensation expense is reduced for estimated forfeitures based on historical experience as well as future expectations. Forfeitures are required to be estimated at the time of grant and revised, if necessary, in subsequent periods if estimated and actual forfeitures differ from these initial estimates. The Company evaluates the assumptions used to value share-based awards on a periodic basis. The Company recognizes stock-based compensation expense based on the graded, or accelerated multiple-option, approach over the vesting period. The Company has outstanding share-based awards that have performance-based vesting conditions. Awards with performance-based vesting conditions require the achievement of certain financial or other performance criteria as a condition to vesting. The Company recognizes the estimated fair value of performance-based awards, net of estimated forfeitures, as stock-based compensation expense over the performance period, using the graded approach, based upon its determination of whether it is probable that the performance targets will be achieved. At each reporting period, the Company reassess the probability of achieving the performance criteria and the performance period required to meet those targets. Determining whether the performance criteria will be achieved involves judgment, and the estimate of stock-based compensation expense may be revised periodically based on changes in the probability of achieving the performance criteria. Revisions are reflected in the period in which the estimate is changed. If performance goals are not met, no stock-based compensation expense is recognized, and, to the extent stock-based compensation was previously recognized, such stock-based compensation is reversed.
Income Taxes	Income Taxes The Company accounts for income taxes using the asset and liability method. Deferred taxes are determined based on the differences between the financial statement and tax bases of assets and liabilities, using enacted tax rates in effect for the year in which the differences are expected to reverse. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected more likely than not to be realized. The Company recognizes, in its consolidated financial statements, the impact of tax positions that are more likely than not to be sustained upon examination based on the technical merits of the positions. The Company recognizes interest and penalties related to uncertain tax positions in income tax expense. See Note 9 for additional information.
Earnings (Loss) Per Share	Earnings (Loss) Per Share Basic earnings (loss) per share is computed using the weighted-average number of common shares outstanding during the period. Diluted net income per share gives effect to all potentially dilutive common stock equivalents outstanding during the period. The dilutive effect of share-based awards is reflected in diluted net income per share by application of the treasury stock method, which includes consideration of unamortized share-based compensation expense, the tax benefits recorded in additional paid-in capital and the dilutive effect of in-the-money options and non-vested restricted stock units. Under the treasury stock method, the amount the employee must pay for exercising stock options, unamortized share-based compensation expense and tax benefits are assumed proceeds to be used to repurchase hypothetical shares. Dilutive potential common shares primarily consist of shares underlying the Company's convertible senior notes (in periods prior to 2016), employee stock options, and restricted stock units. See Note 13 for additional information.
Foreign Currency Translation and Transactions	Foreign Currency Translation and Transactions Assets and liabilities of non-U.S. subsidiaries that operate in a local currency environment are translated to U.S. Dollars at exchange rates in effect at the balance sheet date, with the resulting translation adjustments included as a separate component of accumulated other comprehensive income or loss. Income and expense accounts are translated at average exchange rates during the year. Where the U.S. Dollar is the functional currency, certain balance sheet and income statement accounts are remeasured at historical exchange rates and translation adjustments from the re-measurement of the local currency amounts to U.S. Dollars are included in Interest income and other, net .
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) includes all changes in equity (net assets) during a period from non-owner sources. Accumulated other comprehensive income or loss includes unrealized gains and losses on investments and foreign currency translation adjustments.
Segments	Segments Operating segments are defined as components of an enterprise engaged in business activities for which discrete financial information is available and regularly reviewed by the chief operating decision maker (“CODM”) of the enterprise to make decisions about resource allocation and in assessing performance. The Company's CODM is its Chief Executive Officer who reviews the Company's consolidated budgets and results for the purposes of allocating resources and evaluating financial performance. Accordingly, the Company has determined that it operated within one business segment as of, and for the years ended, December 31, 2016 , 2015 , and 2014 . See Note 5 for entity-wide disclosures about products and services, geographic areas, and major customers.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In January 2017, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2017-14, Simplifying the Test for Goodwill Impairment. ASU 2017-04 removes the requirement for an entity to calculate the implied fair value of goodwill (which is step 2 under the current goodwill impairment guidance) in measuring a goodwill impairment loss. The standard will be effective for annual reporting periods beginning after December 15, 2019, including interim periods within those reporting periods. Early adoption is permitted. The Company has not yet evaluated the impact of the adoption of this accounting standard update on its consolidated financial statements. In October 2016, the FASB issued ASU 2016-16, Intra-Entity Transfers of Assets of Other Than Inventory. Current GAAP prohibits the recognition of current and deferred income taxes for an intra-entity asset transfer until the asset has been sold to an outside party. ASU 2016-16 updates the current guidance by requiring that entities recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. The amendments in this ASU do not change GAAP for the pre-tax effects of an intra-entity asset transfer under Topic 810, Consolidation , or for the income tax effects of an intra-entity transfer of inventory. The standard will be effective for annual reporting periods beginning after December 15, 2017, including interim periods within those reporting periods. Early adoption is permitted. The Company has not yet evaluated the impact of the adoption of this accounting standard update on its consolidated financial statements. In August 2016, the FASB issued ASU 2016-15, Classification of Certain Cash Receipts and Cash Payments - a consensus of the Emerging Task Force. ASU 2016-15 provides guidance on how certain cash receipts and payments are presented and classified in the statement of cash flows, including debt prepayment or debt extinguishment costs, contingent consideration payments made after a business combination, and separately identifiable cash flows, and application of the predominance principle. The standard is intended to reduce current diversity in practice. The standard will be effective for annual reporting periods beginning after December 15, 2017, including interim periods within those reporting periods. Early adoption is permitted. The Company has not yet evaluated the impact of the adoption of this accounting standard update on its consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses: Measurement of Credit Losses on Financial Instruments. ASU 2016-13 replaces the incurred loss impairment methodology in current GAAP with a methodology that reflects expected credit losses. The update is intended to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. The standard will be effective for annual reporting periods beginning after December 15, 2019, including interim periods within those reporting periods. Early adoption is permitted. The Company has not yet evaluated the impact of the adoption of this accounting standard update on its consolidated financial statements. In May 2016, the FASB issued ASU 2016-12, Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients. ASU 2016-12 addresses narrow-scope improvements to the guidance on collectibility, non-cash consideration, and completed contracts at transition. Additionally, the amendments in this update provide a practical expedient for contract modifications at transition and an accounting policy election related to the presentation of sales taxes and other similar taxes collected from customers. The amendments in this update affect the guidance in ASU 2014-09, Revenue from Contracts with Customers, which is not yet effective. The effective date and transition requirements for the amendments in this update are the same as the effective date and transition requirements of ASU 2014-09 (as discussed below). In April 2016, the FASB issued ASU 2016-10, Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing. ASU 2016-10 clarifies the implementation guidance on identifying performance obligations and licensing. Specifically, the amendments reduce the cost and complexity of identifying promised goods or services and improve the guidance for determining whether promises are separately identifiable. The amendments also provide implementation guidance on determining whether an entity's promise to grant a license provides a customer with either a right to use the entity's intellectual property (which is satisfied at a point in time) or a right to access the entity's intellectual property (which is satisfied over time). The amendments in this update affect the guidance in ASU 2014-09, Revenue from Contracts with Customers, which is not yet effective. The effective date and transition requirements for the amendments in this update are the same as the effective date and transition requirements of ASU 2014-09 (as discussed below). In March 2016, the FASB issued ASU 2016-09, Compensation–Stock Compensation: Improvements to Employee Share-Based Payment Accounting. ASU 2016-09 involves several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. Under the new standard, income tax benefits and deficiencies are to be recognized as income tax expense or benefit in the income statement and the tax effects of exercised or vested awards should be treated as discrete items in the reporting period in which they occur. An entity should also recognize excess tax benefits regardless of whether the benefit reduces taxes payable in the current period. Excess tax benefits should be classified along with other income tax cash flows as an operating activity. In regards to forfeitures, the entity may make an entity-wide accounting policy election to either estimate the number of awards that are expected to vest or account for forfeitures when they occur. The standard will be effective for annual reporting periods beginning after December 15, 2016, including interim periods within those reporting periods. The manner of application varies based on the various provisions of the guidance, with certain provisions applied on a retrospective or modified retrospective approach, while others are applied prospectively. The guidance related to forfeitures will be adopted by the Company under a modified retrospective transition method and a cumulative adjustment to beginning retained earnings will be recorded on the day of adoption. Effective January 1, 2017, the Company will account for forfeitures as they occur. The new standard may cause volatility in the Company's effective tax rates and diluted earnings per share amounts due to the tax effects related to share-based payments being recorded to the income statement. The volatility in future periods will depend on our stock price at the awards’ vest or exercise date and the number of awards that vest or are exercised in each period. In March 2016, the FASB issued ASU 2016-08, Revenue from Contracts with Customers: Principal Versus Agent Considerations. ASU 2016-08 clarifies the implementation guidance for what the FASB calls principal-versus-agent considerations in the board's revenue recognition standard by instructing the participants in the sale to determine whether they control the good or service and are entitled to the gross amount of the transaction or are acting as an agent and should collect only a fee or commission for arranging the sale. The amendments in this update affect the guidance in ASU 2014-09, Revenue from Contracts with Customers, which is not yet effective. The effective date and transition requirements for the amendments in this update are the same as the effective date and transition requirements of ASU 2014-09 (as discussed below). In February 2016, the FASB issued ASU 2016-02, Leases , which requires that lessees recognize assets and liabilities for leases with lease terms greater than twelve months in the statement of financial position. ASU 2016-02 also requires improved disclosures to help users of financial statements better understand the amount, timing, and uncertainty of cash flows arising from leases . The standard will be effective for annual reporting periods beginning after December 15, 2018, including interim periods within those reporting periods. Early adoption is permitted. The Company has not yet evaluated the impact of the adoption of this accounting standard on its consolidated financial statements. In January 2016, the FASB issued ASU 2016-01, Financial Instruments–Overall: Recognition and Measurement of Financial Assets and Financial Liabilities , which provides updated guidance that enhances the reporting model for financial instruments, which includes amendments to address aspects of recognition, measurement, presentation, and disclosure. The standard will be effective for annual reporting periods beginning after December 15, 2017, including interim periods within those reporting periods. Except for the early application guidance, early adoption of the amendments is not permitted. The Company has not yet evaluated the impact of the adoption of this accounting standard update on its consolidated financial statements. In November 2015, the FASB issued ASU 2015-17, Balance Sheet Classification of Deferred Taxes, to simplify the presentation of deferred taxes in the statement of financial position. The updated guidance requires that deferred tax assets and liabilities be classified as noncurrent in a classified balance sheet. The standard will be effective for annual reporting periods beginning after December 15, 2016, including interim periods within those reporting periods, with early adoption permitted. The ASU may be adopted either prospectively or retrospectively. The Company elected to early adopt this standard in the fourth quarter of 2016 and to apply this standard prospectively. Accordingly, the consolidated balance sheet as of December 31, 2016 reflects the new classification but the prior period amounts were not adjusted to conform to the new guidance. In July 2015, the FASB issued ASU 2015-11, Simplifying the Measurement of Inventory , which provides new guidance regarding the measurement of inventory. The new guidance requires most inventory to be measured at the lower of cost and net realizable value. The standard defines net realizable value as estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The standard applies to companies other than those that measure inventory using last-in, first-out (LIFO) or the retail inventory method. The standard will be effective for annual reporting periods beginning after December 15, 2016, including interim periods within those reporting periods. Early adoption is permitted. The Company does not expect that the adoption of this guidance will have a material impact on its consolidated financial statements. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers, which provides new guidance on the recognition of revenue and states that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The standard was originally set to become effective in annual periods beginning after December 15, 2016 and for interim and annual reporting periods thereafter. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers; Deferral of the Effective Date, which defers the effective date of ASU 2014-09 for all entities by one year, thereby delaying the effective date of the standard to January 1, 2018, with an option that would permit companies to adopt the standard as early as the original effective date. The standard can be applied either retrospectively to each period presented or as a cumulative effect adjustment as of the date of adoption. The Company has not yet selected a transition method. While the Company is continuing to assess all potential impacts of the new standard, it currently believes the most significant impact relates to certain accounting for arrangements that include sales of software that are bundled with maintenance and support and/or professional services, where VSOE has not been established for the maintenance and support and/or the professional services. Under current GAAP, the revenue attributable to these software sales is typically deferred and recognized as the applicable services are delivered or when the services are completed depending on the arrangement because VSOE does not exist for the undelivered maintenance and support and/or professional services elements. The requirement to have VSOE for undelivered elements to enable the separation of revenue for the delivered software is eliminated under the new standard. Accordingly, under the new standard the Company will be required to recognize as revenue a portion of the arrangement fee upon delivery of the software sold. Due to the complexity of certain of the Company's contracts, the actual revenue recognition treatment required under the new standard for these arrangements may be dependent on contract-specific terms and vary in some instances. The Company is also evaluating the impact of ASU 2014-09 on its sales commission costs. Under current GAAP, the Company records sales commissions as earned; however, under the new standard, sales commission costs will generally need to be capitalized and amortized over the period of contract performance.

Description of Business, Basi25

Description of Business, Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements (Tables)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Schedule of Activity in Product Warranty Liability Account	Activity in the product warranty liability account for the years presented is as follows (in thousands): December 31, December 31, December 31, Balance at beginning of year $ 538 $ 716 $ 646 Current year provision 1,972 2,072 1,759 Expenditures (2,193 ) (2,250 ) (1,689 ) Balance at end of year $ 317 $ 538 $ 716

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2016
Business Combinations [Abstract]
Summary of the Allocation of the Purchase Price to the Estimated Fair Value of the Assets Acquired and Liabilities Assumed	The following table summarizes the final allocation of the purchase price to the estimated fair values of the assets acquired and liabilities assumed at the date of acquisition (in thousands): Cash and cash equivalents $ 1,967 Accounts receivable 9,253 Inventories 6,543 Prepaid and other assets 1,742 Fixed assets, 2,976 Deferred tax asset 26,915 Identifiable intangible assets 72,858 Goodwill 78,727 Total assets acquired 200,981 Accounts payable, accrued expenses and other liabilities (8,440 ) Deferred revenues (5,170 ) Net assets acquired $ 187,371

Restructuring Costs (Tables)

Restructuring Costs (Tables)	12 Months Ended
	Dec. 31, 2016
Restructuring and Related Activities [Abstract]
Schedule of Activities Related to Restructuring Plans	Activities related to the Company's restructuring plans are as follows (in thousands): Restructuring Prior to 2014 Net Optics Restructuring 2014 Corporate Restructuring Other Restructuring Total Accrual at December 31, 2013 $ 1,507 $ — $ — $ — $ 1,507 Charges 136 3,852 6,322 — 10,310 Payments (1,391 ) (3,515 ) (4,382 ) — (9,288 ) Non-cash items (6 ) — — — (6 ) Accrual at December 31, 2014 246 337 1,940 — 2,523 Credits — (322 ) (195 ) — (517 ) Payments (140 ) (15 ) (1,304 ) — (1,459 ) Non-cash items (106 ) — — — (106 ) Accrual at December 31, 2015 — — 441 — 441 (Credits) charges — — (319 ) 189 (130 ) Payments — — 317 — 317 Non-cash items — — (133 ) — (133 ) Accrual at December 31, 2016 $ — $ — $ 306 $ 189 $ 495

Concentrations (Tables)

Concentrations (Tables)	12 Months Ended
	Dec. 31, 2016
Risks and Uncertainties [Abstract]
Schedule of Revenue by Product Line	The following table presents revenue by product line (in thousands): Year Ended December 31, 2016 2015 2014 Network Test Solutions $ 349,557 $ 386,614 $ 345,673 Network Visibility Solutions 135,288 130,323 118,785 Total $ 484,845 $ 516,937 $ 464,458
Schedule of Concentration Risk, by Risk Factor	For the years ended December 31, 2016 , 2015 , and 2014 , total international revenues as a percentage of total revenues based on customer location consisted of the following: Year Ended December 31, 2016 2015 2014 International revenues 43.6 % 38.5 % 40.8 %
Schedule of Property and Equipment, Net by Geographical Location	As of December 31, 2016 and 2015 , property and equipment, net were geographically located as follows (in thousands): As of December 31, 2016 2015 United States $ 22,974 $ 23,654 Romania 6,482 6,542 India 3,385 3,576 Other 3,825 2,764 Total $ 36,666 $ 36,536

Selected Balance Sheet Data (Ta

Selected Balance Sheet Data (Tables)	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Activity in the Allowance for Doubtful Accounts	Activity in allowance for doubtful accounts during the years presented is as follows (in thousands): December 31, December 31, December 31, Balance at beginning of year $ 1,107 $ 1,011 $ 840 Additions: charged to costs and expenses 416 525 275 Deductions: write-offs, net of recoveries (612 ) (429 ) (104 ) Balance at end of year $ 911 $ 1,107 $ 1,011
Schedule of Investments in Marketable Securities	Investments in marketable securities as of December 31, 2016 consisted of the following (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Available-for-sale – short-term: U.S. Treasury, government, and agency debt securities $ 37,002 $ 24 $ (21 ) $ 37,005 Corporate debt securities 34,292 8 (54 ) 34,246 Total $ 71,294 $ 32 $ (75 ) $ 71,251 Investments in marketable securities as of December 31, 2015 consisted of the following (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Available-for-sale – short-term: U.S. Treasury, government, and agency debt securities $ 4,301 $ — $ (13 ) $ 4,288 Corporate debt securities 10,265 — (49 ) 10,216 Total $ 14,566 $ — $ (62 ) $ 14,504
Schedule of Amortized Cost and Fair Value of Investments	The amortized cost and fair value of our investments at December 31, 2016 , by contractual years-to-maturity, are as follows (in thousands): Amortized Cost Fair Value Due in less than 1 year $ 34,715 $ 34,706 Due within 1-2 years 20,928 20,928 Due within 2-5 years 10,051 10,017 Due after 5 years 5,600 5,600 Total $ 71,294 $ 71,251
Schedule of Inventories	Inventories consisted of the following (in thousands): December 31, December 31, Raw materials $ 1,252 $ 3,864 Work in process 6,581 11,253 Finished goods 20,824 18,172 Total $ 28,657 $ 33,289
Schedule of Property and Equipment, Net	Property and equipment, net consisted of the following (dollars in thousands): December 31, December 31, Useful Life (in years) Development equipment 5 $ 39,312 $ 35,831 Demonstration equipment 2 32,543 29,258 Furniture and other equipment 5 23,497 22,066 Computer software 3 - 5 22,803 20,702 Building and leasehold improvements 1 - 40 22,574 20,921 Computer equipment 3 17,929 16,698 Total 158,658 145,476 Accumulated depreciation (121,992 ) (108,940 ) Total $ 36,666 $ 36,536
Schedule of Accrued Expenses and Other	Accrued expenses and other consisted of the following (in thousands): December 31, December 31, Compensation and related expenses $ 12,428 $ 12,805 Vacation 5,724 7,967 Commissions 4,711 5,083 Professional fees 3,409 2,163 Other taxes 2,651 3,106 Bonuses 2,202 20,423 Legal contingencies 750 4,825 Income taxes 707 3,599 Other 6,820 10,058 Total $ 39,402 $ 70,029

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Summary of Financial Assets Carried at Fair Value	Financial assets carried at fair value as of December 31, 2016 and 2015 are summarized below (in thousands): December 31, 2016 December 31, 2015 Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents: Money market funds $ 769 $ 769 $ — $ — $ 284 $ 284 $ — $ — Corporate debt securities 7,943 — 7,943 — — — — — Marketable securities: U.S. Treasury, government and agency debt securities 37,005 — 37,005 — 4,288 — 4,288 — Corporate debt securities 34,246 — 34,246 — 10,216 — 10,216 — Total financial assets $ 79,963 $ 769 $ 79,194 $ — $ 14,788 $ 284 $ 14,504 $ —

Goodwill and Other Intangible31

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Purchased Intangible Assets	The following table presents the Company's purchased intangible assets (in thousands) as of December 31, 2016 : Weighted Average Useful Life Gross Accumulated Amortization Net (in years) Other intangible assets: Technology 5.5 $ 185,665 $ (151,672 ) $ 33,993 Customer relationships 6.0 71,700 (59,659 ) 12,041 Service agreements 6.4 30,100 (17,968 ) 12,132 Trademark 5.1 11,300 (8,966 ) 2,334 Non-compete agreements 4.0 8,000 (7,142 ) 858 Other 4.7 6,866 (2,547 ) 4,319 Total $ 313,631 $ (247,954 ) $ 65,677 The following table presents the Company's purchased intangible assets (in thousands) as of December 31, 2015 : Weighted Average Useful Life Gross Accumulated Amortization Net (in years) Other intangible assets: Technology 5.5 $ 185,665 $ (129,509 ) $ 56,156 Customer relationships 6.0 71,700 (51,533 ) 20,167 Service agreements 6.4 30,100 (13,272 ) 16,828 Trademark 5.1 11,300 (7,000 ) 4,300 Non-compete agreements 4.0 8,000 (5,641 ) 2,359 Other 4.5 5,750 (1,900 ) 3,850 Total $ 312,515 $ (208,855 ) $ 103,660
Schedule of Estimated Future Amortization Expense	The estimated future amortization expense of purchased intangible assets as of December 31, 2016 is as follows (in thousands): 2017 $ 31,930 2018 20,666 2019 7,434 2020 3,892 2021 700 Thereafter 1,055 Total $ 65,677

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Components of Income Before Income Taxes	The components of income before income taxes were (in thousands): Year Ended December 31, 2016 2015 2014 U.S. $ (13,895 ) $ (5,307 ) $ (53,850 ) Foreign 30,684 19,650 1,153 Total $ 16,789 $ 14,343 $ (52,697 )
Schedule of Income Tax Expense (Benefit)	Income tax expense (benefit) consisted of the following (in thousands): Year Ended December 31, 2016 2015 2014 Current: Federal $ 7,260 $ 10,150 $ (372 ) State 684 1,635 1,111 Foreign 5,560 4,273 2,538 Deferred: Federal 25,981 (5,145 ) (12,479 ) State 11,299 (1,044 ) (1,916 ) Foreign (84 ) (1,477 ) 13 Income tax expense (benefit) $ 50,700 $ 8,392 $ (11,105 )
Schedule of Net Effective Income Tax Rate	The net effective income tax rate differed from the federal statutory income tax rate of 35% as follows (dollars in thousands): 2016 2015 2014 Federal statutory expense $ 5,876 $ 5,020 $ (18,445 ) State taxes, net of federal benefit 11,866 269 (805 ) Research and development credits (1,603 ) (1,177 ) (1,585 ) Domestic production deduction (236 ) (595 ) — Foreign branch losses (2 ) 90 (1,213 ) Stock-based compensation 1,507 1,740 1,700 Foreign rate differential (5,463 ) (3,240 ) 1,633 Inter-company royalty 2,964 3,121 3,168 Inter-company transfer 1,994 1,994 1,841 Valuation allowance 31,077 (1,939 ) — Unrecognized tax benefits 1,157 1,160 1,497 Other 1,563 1,949 1,104 Income tax expense (benefit) $ 50,700 $ 8,392 $ (11,105 ) Net effective income tax rate 302.0 % 58.5 % 21.1 %
Primary Components of Temporary Differences	The primary components of temporary differences that gave rise to deferred taxes were as follows (in thousands): December 31, December 31, Deferred tax assets: Research and development credit carryforward $ 13,734 $ 13,544 Deferred revenue 6,272 3,611 Stock-based compensation 11,474 10,674 Inventory adjustments 6,651 8,862 Net operating loss carryforward 4,331 4,939 Realized loss on investments 1,069 3,421 Accrued liabilities and other 1,117 1,056 Depreciation and amortization 5,894 958 Allowance for doubtful accounts 228 282 50,770 47,347 Valuation allowance (45,000 ) (2,056 ) 5,770 45,291 Deferred tax liabilities: Depreciation and amortization (202 ) (382 ) Intercompany royalty (10,537 ) (11,852 ) Net deferred tax (liabilities) assets $ (4,969 ) $ 33,057
Reconciliation of Gross Unrecognized Tax Benefits	A reconciliation of the beginning and ending amounts of gross unrecognized tax benefits is as follows (in thousands): 2016 2015 2014 Unrecognized tax benefits - beginning balance $ 21,178 $ 19,134 $ 16,766 Gross increases – tax positions taken in prior period 50 188 417 Gross decreases – tax positions taken in prior period (51 ) (161 ) (74 ) Gross increases – tax positions taken in current period 2,515 2,017 2,167 Lapse of statute of limitations (166 ) — (142 ) Unrecognized tax benefits – ending balance $ 23,526 $ 21,178 $ 19,134

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Commitments Under Leases	The following are the future minimum commitments under these leases (in thousands): Year Ending December 31,* 2017 $ 11,849 2018 11,161 2019 9,496 2020 8,029 2021 5,290 Thereafter 8,282 Total $ 54,107 *Minimum payments have not been reduced by minimum sublease rentals of $43,000 due in the future under non-cancelable subleases.

Shareholders_ Equity (Tables)

Shareholders’ Equity (Tables)	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Summary of Stock Option Activity	The following table summarizes stock option activity for the year ended December 31, 2016 (in thousands, except per share and contractual life data): Number of Options Weighted Average Exercise Price Per Share Weighted Average Remaining Contractual Life (in years) Aggregate Intrinsic Value Outstanding as of December 31, 2015 5,474 $ 12.11 4.35 $ 9,350 Granted 1,240 11.30 Exercised (775 ) 8.68 Forfeited/canceled (459 ) 14.56 Outstanding as of December 31, 2016 5,480 $ 12.21 4.34 $ 22,638 Vested and expected to vest as of December 31, 2016 5,336 $ 12.23 4.30 $ 21,933 Exercisable at December 31, 2016 3,395 $ 12.96 3.56 $ 11,950
Summary of RSU Activity	The following table summarizes RSU activity for the year ended December 31, 2016 (in thousands, except per share data): Number of Awards Weighted Average Grant Date Fair Value Per Share Outstanding as of December 31, 2015 1,963 $ 12.63 Awarded 1,114 11.70 Vested (730 ) 13.10 Forfeited/canceled (188 ) 12.13 Outstanding as of December 31, 2016 2,159 $ 12.03
Schedule of Weighted Average Assumptions Used to Calculate Estimated Fair Value	The Black-Scholes option-pricing model is used to calculate the estimated fair value of share-based awards for options and RSUs on the respective dates of grant for accounting purposes using the following weighted average assumptions: Year Ended December 31, 2016 2015 2014 Expected lives (in years) 4.0 3.9 4.0 Risk-free interest rates 1.1 % 1.2 % 1.2 % Dividend yield — % — % — % Expected volatility 37.4 % 43.3 % 46.7 % The Black-Scholes option-pricing model is used to calculate the estimated fair value of share-based awards for our Purchase Plan for accounting purposes using the following weighted average assumptions: Year Ended December 31, 2016 2015 2014 Expected lives (in years) 1.3 1.3 1.2 Risk-free interest rates 0.6 % 0.4 % 0.2 % Dividend yield — % — % — % Expected volatility 35.7 % 28.4 % 32.9 %
Schedule Stock-Based Compensation by Award Type	Our stock-based compensation by award type is as follows (in thousands): Year Ended December 31, 2016 2015 2014 Options $ 4,438 $ 5,032 $ 3,934 RSUs 11,267 10,078 9,328 Common shares issued under the Purchase Plan 3,002 3,866 3,257 Total stock-based compensation $ 18,707 $ 18,976 $ 16,519
Summary of Changes in Accumulated Other Comprehensive Loss	The following table summarizes, as of each balance sheet date, the changes in the Company's accumulated other comprehensive loss, by component, net of income taxes (in thousands): Unrealized Gains and Losses on Available-for- Sale Securities (a) Foreign Currency Items (a) Total Beginning balance, December 31, 2014 $ (32 ) $ (761 ) $ (793 ) Other comprehensive loss before reclassifications (76 ) (184 ) (260 ) Amounts reclassified from accumulated other comprehensive loss (b) 20 — 20 Net current-period other comprehensive loss (56 ) (184 ) (240 ) Ending balance, December 31, 2015 $ (88 ) $ (945 ) $ (1,033 ) Other comprehensive gain before reclassifications 75 63 138 Amounts reclassified from accumulated other comprehensive loss (b) (13 ) — (13 ) Net current-period other comprehensive gain 62 63 125 Ending balance, December 31, 2016 $ (26 ) $ (882 ) $ (908 ) (a) All amounts are net-of-tax. Amounts in parentheses indicate reductions. (b) Amount represents gain on the sale of securities and is included as a component of Interest income and other, net in the consolidated statements of operations.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Computation of Basic and Diluted Earnings (Loss) Per Share	The following table sets forth the computation of basic and diluted earnings (loss) per share for the periods indicated (in thousands, except per share data): Year Ended December 31, 2016 2015 2014 Basic Presentation: Numerator for basic (loss) earnings per share: Net (loss) income $ (33,911 ) $ 5,951 $ (41,592 ) Denominator for basic (loss) earnings per share: Weighted average common shares outstanding 81,470 79,633 77,629 Basic (loss) earnings per share $ (0.42 ) $ 0.07 $ (0.54 ) Diluted presentation: Numerator for diluted (loss) earnings per share: Net (loss) income $ (33,911 ) $ 5,951 $ (41,592 ) Denominator for diluted (loss) earnings per share: Weighted average common shares outstanding 81,470 79,633 77,629 Effect of dilutive securities: Stock options and other share-based awards — 1,826 — Dilutive potential common shares 81,470 81,459 77,629 Diluted (loss) earnings per share $ (0.42 ) $ 0.07 $ (0.54 )

Quarterly Financial Summary (36

Quarterly Financial Summary (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Summary	For the three months ended 2016 2015 Dec. 31 Sep. 30 Jun. 30 Mar. 31 Dec. 31 Sep. 30 Jun. 30 Mar. 31 (in thousands) Consolidated Statement of Operations Data: Total revenues $ 128,163 $ 123,911 $ 120,098 $ 112,673 $ 138,478 $ 125,887 $ 131,610 $ 120,962 Total cost of revenues (1) 33,558 33,352 30,343 31,660 35,697 33,913 34,983 35,001 Gross profit 94,605 90,559 89,755 81,013 102,781 91,974 96,627 85,961 Income (loss) before income taxes 6,949 6,560 8,249 (4,969 ) 12,309 506 6,574 (5,046 ) Net (loss) income (2) (37,520 ) 4,773 1,523 (2,687 ) 5,751 4,008 5,803 (9,611 ) (Loss) earnings per share: Basic $ (0.46 ) $ 0.06 $ 0.02 $ (0.03 ) $ 0.07 $ 0.05 $ 0.07 $ (0.12 ) Diluted $ (0.46 ) $ 0.06 $ 0.02 $ (0.03 ) $ 0.07 $ 0.05 $ 0.07 $ (0.12 ) (1) For the quarters ended: December 31, 2016 ; September 30, 2016 ; June 30, 2016 ; March 31, 2016 ; December 31, 2015 ; September 30, 2015 ; June 30, 2015 ; and March 31, 2015 ; total cost of revenues includes charges related to amortization of intangible assets of $6.2 million , $6.3 million , $6.4 million , $6.4 million , $6.4 million , $6.4 million , $6.4 million , and $6.4 million , respectively. (2) In the quarter ended December 31, 2016 , income tax expense includes a $42.9 million charge related to the establishment of a valuation allowance against the Company's remaining net deferred tax assets in the U.S.

Description of Business, Basi37

Description of Business, Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements - Foreign Currency Forward Contracts (Narrative) (Details) - Foreign Exchange Forward $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)contract	Dec. 31, 2015USD ($)contract	Dec. 31, 2014USD ($)
Derivative [Line Items]
Number of foreign currency forward contracts | contract	4	3
Notional amount	$ 3,900	$ 4,800
Asset fair value	7	15
Net (losses) gains related to the change in fair value	$ (54)	$ 208	$ 531

Description of Business, Basi38

Description of Business, Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements - Property, Plant and Equipment (Narrative) (Details)	12 Months Ended
	Dec. 31, 2016
Minimum
Property, Plant and Equipment [Line Items]
Useful Life	3 years
Maximum
Property, Plant and Equipment [Line Items]
Useful Life	5 years
Development equipment
Property, Plant and Equipment [Line Items]
Useful Life	5 years
Products Used for Sales and Marketing
Property, Plant and Equipment [Line Items]
Useful Life	2 years

Description of Business, Basi39

Description of Business, Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements - Goodwill (Narrative) (Details)	12 Months Ended
	Dec. 31, 2016USD ($)
Accounting Policies [Abstract]
Impairment	$ 0

Description of Business, Basi40

Description of Business, Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements - Product Warranty (Narrative) (Details)	12 Months Ended
	Dec. 31, 2016
Minimum
Product Warranty Liability [Line Items]
Initial standard warranty, term	90 days
Maximum
Product Warranty Liability [Line Items]
Initial standard warranty, term	12 months

Description of Business, Basi41

Description of Business, Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements - Schedule of Activity in Product Warranty Liability Account (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Movement in Standard Product Warranty Accrual
Balance at beginning of year	$ 538	$ 716	$ 646
Current year provision	1,972	2,072	1,759
Expenditures	(2,193)	(2,250)	(1,689)
Balance at end of year	$ 317	$ 538	$ 716

Description of Business, Basi42

Description of Business, Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements - Revenue Recognition (Narrative) (Details)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Service period	1 year

Description of Business, Basi43

Description of Business, Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements - Multiple Element Arrangements and Allocation of Value (Narrative) (Details)	12 Months Ended
	Dec. 31, 2016
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Substantial majority of transactions priced within a reasonably narrow range (as a percent)	75.00%
Reasonably narrow range (as a percent)	15.00%
Minimum
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Initial period of free technical support, warranty and software maintenance services	90 days
Maximum
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Initial period of free technical support, warranty and software maintenance services	12 months

Description of Business, Basi44

Description of Business, Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements - Cost of Revenues (Narrative) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization excluded from cost of revenues	[1]	$ 39,099	$ 42,315	$ 46,901
Intangible assets related to purchased technologies
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization excluded from cost of revenues		$ 25,300	$ 25,700	$ 28,900
[1]	Stock-based compensation included in:Cost of revenues – products$280 $315 $331Cost of revenues – services108 120 126Research and development6,489 6,625 6,843Sales and marketing5,944 4,730 5,624General and administrative5,886 7,186 3,595

Description of Business, Basi45

Description of Business, Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements - Shipping and Handling Costs (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Shipping and handling costs	$ 1.4	$ 1.3	$ 1.7

Description of Business, Basi46

Description of Business, Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements - Software Developed for Internal Use (Narrative) (Details)	12 Months Ended
	Dec. 31, 2016
Internally developed software
Property, Plant and Equipment [Line Items]
Amortization period	5 years

Description of Business, Basi47

Description of Business, Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements - Advertising (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Advertising costs included in Sales and marketing	$ 3.6	$ 2.4	$ 2.6

Description of Business, Basi48

Description of Business, Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements - Foreign Currency Translation and Transactions (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Net foreign currency losses	$ 845	$ 1,300	$ 767

Description of Business, Basi49

Description of Business, Basis of Presentation, Significant Accounting Policies and Recent Accounting Pronouncements - Segments (Narrative) (Details)	12 Months Ended
	Dec. 31, 2016segment
Accounting Policies [Abstract]
Number of business segments	1

Acquisitions - Additional Infor

Acquisitions - Additional Information (Details) - USD ($) $ in Thousands		Dec. 05, 2013	Dec. 31, 2014	Mar. 31, 2014	Sep. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Acquisition and other related costs	[1]					$ 785	$ 656	$ 3,277
Net Optics Inc
Business Acquisition [Line Items]
Purchase price		$ 187,400	$ 187,400	$ 187,700
Acquisition and other related costs							$ 663
Increase to deferred tax assets		26,900
Adjustment to value of accrued expenses and other liabilities and goodwill balances			$ 341
Identifiable intangible assets		72,858
Net Optics Inc | Scenario, Previously Reported
Business Acquisition [Line Items]
Purchase price					$ 187,700				$ 193,800
Net Optics Inc | Scenario, Adjustment
Business Acquisition [Line Items]
Purchase price		(6,100)
Net Optics Inc | Minimum
Business Acquisition [Line Items]
Expected useful lives						4 months
Net Optics Inc | Maximum
Business Acquisition [Line Items]
Expected useful lives						7 years
Net Optics Inc | Acquired technology
Business Acquisition [Line Items]
Identifiable intangible assets		50,000
Net Optics Inc | Customer relationships
Business Acquisition [Line Items]
Identifiable intangible assets		15,800
Net Optics Inc | Non-compete agreements
Business Acquisition [Line Items]
Identifiable intangible assets		3,700
Net Optics Inc | Trade names
Business Acquisition [Line Items]
Identifiable intangible assets		3,000
Net Optics Inc | Other identifiable intangible assets
Business Acquisition [Line Items]
Identifiable intangible assets		$ 358
[1]	Stock-based compensation included in:Cost of revenues – products$280 $315 $331Cost of revenues – services108 120 126Research and development6,489 6,625 6,843Sales and marketing5,944 4,730 5,624General and administrative5,886 7,186 3,595

Acquisitions - Summary of the A

Acquisitions - Summary of the Allocation of the Purchase Price to the Estimated Fair Value of the Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 05, 2013
Business Acquisition [Line Items]
Goodwill	$ 338,873	$ 338,873
Net Optics Inc
Business Acquisition [Line Items]
Cash and cash equivalents			$ 1,967
Accounts receivable			9,253
Inventories			6,543
Prepaid and other assets			1,742
Fixed assets,			2,976
Deferred tax asset			26,915
Identifiable intangible assets			72,858
Goodwill			78,727
Total assets acquired			200,981
Accounts payable, accrued expenses and other liabilities			(8,440)
Deferred revenues			(5,170)
Net assets acquired			$ 187,371

Debt - 2015 Credit Agreement (D

Debt - 2015 Credit Agreement (Details) - USD ($)	Mar. 02, 2015	Sep. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016	Jan. 25, 2016
Debt Instrument [Line Items]
Amortization recorded to interest expense pertaining to deferred issuance costs			$ 452,000	$ 1,500,000	$ 1,870,000
Credit Agreement | Collateral A
Debt Instrument [Line Items]
Available liquidity			$ 50,000,000			$ 50,000,000
Term Loan | 2015 Credit Agreement [Member]
Debt Instrument [Line Items]
Aggregate principal amount of term loan	$ 40,000,000
Quarterly repayments	$ 500,000
Fixed charge coverage ratio			1.25
Consolidated total leverage ratio			3.25
Consolidated senior leverage ratio			3
Term Loan | 2015 Credit Agreement [Member] | Eurodollar
Debt Instrument [Line Items]
Interest rate (as a percent)		4.25%
Weighted average interest rate applicable to the Term Loan			2.57%
Interest rate applicable to the amount outstanding under the Term Loan			2.61%			2.61%
Term Loan | 2015 Credit Agreement [Member] | Base Rate
Debt Instrument [Line Items]
Interest rate (as a percent)		3.25%
Term Loan | 2015 Credit Agreement [Member] | First-tier foreign subsidiaries
Debt Instrument [Line Items]
Interest in subsidiary (as a percent)	65.00%
Term Loan | 2015 Credit Agreement [Member] | Ixia Technologies International Limited
Debt Instrument [Line Items]
Interest in subsidiary (as a percent)	65.00%
Term Loan | 2015 Credit Agreement [Member] | Minimum
Debt Instrument [Line Items]
Quarterly repayments			$ 1,000,000			$ 1,000,000
Commitment fee (as a percent)			0.30%
Term Loan | 2015 Credit Agreement [Member] | Minimum | Eurodollar
Debt Instrument [Line Items]
Interest rate (as a percent)						2.00%
Term Loan | 2015 Credit Agreement [Member] | Minimum | Base Rate
Debt Instrument [Line Items]
Interest rate (as a percent)						1.00%
Term Loan | 2015 Credit Agreement [Member] | Maximum
Debt Instrument [Line Items]
Quarterly repayments			$ 1,500,000			$ 1,500,000
Commitment fee (as a percent)			0.50%
Term Loan | 2015 Credit Agreement [Member] | Maximum | Eurodollar
Debt Instrument [Line Items]
Interest rate (as a percent)						3.00%
Term Loan | 2015 Credit Agreement [Member] | Maximum | Base Rate
Debt Instrument [Line Items]
Interest rate (as a percent)						2.00%
Revolving Credit Facility | Revolving credit facility | Silicon Valley Bank
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 60,000,000	$ 75,000,000					$ 150,000,000
Amount limit is subject to increase by							$ 100,000,000
Debt issuance costs	2,200,000
Amortization recorded to interest expense pertaining to deferred issuance costs			$ 452,000	$ 376,000
Maximum amount allowed to fund cash acquisitions			$ 200,000,000			$ 200,000,000
Revolving Credit Facility | Revolving credit facility | Silicon Valley Bank | Upon Default
Debt Instrument [Line Items]
Interest rate (as a percent)			2.00%
Revolving Credit Facility | Revolving credit facility | Minimum | Silicon Valley Bank | Leverage Ratio
Debt Instrument [Line Items]
Interest rate (as a percent)			2.00%
Revolving Credit Facility | Revolving credit facility | Maximum | Silicon Valley Bank | Leverage Ratio
Debt Instrument [Line Items]
Interest rate (as a percent)			3.00%
Revolving Credit Facility | Standby letters of credit | Silicon Valley Bank
Debt Instrument [Line Items]
Maximum borrowing capacity	25,000,000
Revolving Credit Facility | Swingline loans | Silicon Valley Bank
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 15,000,000

Debt - Unsecured Convertible Se

Debt - Unsecured Convertible Senior Notes (Details) - USD ($)	1 Months Ended		12 Months Ended
	Dec. 31, 2015	Jul. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 07, 2010
Debt Instrument [Line Items]
Amortization of deferred issuance costs recorded to interest expense			$ 452,000	$ 1,500,000	$ 1,870,000
Convertible Senior Notes | Convertible Notes Payable
Debt Instrument [Line Items]
Aggregate principal amount of Convertible Senior Notes	$ 135,000,000			135,000,000		$ 200,000,000
Stated rate (as a percent)						3.00%
Repayments of debt	$ 2,000,000
Amortization of deferred issuance costs recorded to interest expense				$ 1,300,000	$ 1,200,000
Convertible Senior Notes | Convertible Notes Payable | Convertible Debt
Debt Instrument [Line Items]
Repurchased aggregate principal amount		$ 65,000,000
Aggregate cash purchase price		65,200,000
Accrued interest		$ 119,000

Restructuring Costs - Narrative

Restructuring Costs - Narrative (Details) $ in Thousands		3 Months Ended		12 Months Ended
		Sep. 30, 2014position	Mar. 31, 2014position	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Restructuring Cost and Reserve [Line Items]
Net restructuring credits	[1]			$ 130	$ 517	$ (10,310)
Restructuring charges				200	143
Restructuring credits				300	660
Recoveries relating to favorable lease buyout					371
Recoveries relating to receipt of proceeds from insurance settlement					382
Remaining accrual related to restructuring activities				495	441	2,523	$ 1,507
Net Optics Restructuring And 2014 Corporate Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges						10,300
Net Optics Restructuring
Restructuring Cost and Reserve [Line Items]
Net restructuring credits				0	322	(3,852)
Restructuring charges						3,500
Number of positions | position			45
Percentage of Company's worldwide workforce			2.30%
Remaining accrual related to restructuring activities				0	0	337	0
Net Optics Restructuring | Severance and other employee related costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges						2,000
Net Optics Restructuring | Facility related charges
Restructuring Cost and Reserve [Line Items]
Restructuring charges						1,200
Net Optics Restructuring | Other Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring charges						316
2014 Corporate Restructuring
Restructuring Cost and Reserve [Line Items]
Net restructuring credits				319	195	(6,322)
Restructuring charges						6,100
Number of positions | position		96
Percentage of Company's worldwide workforce		5.00%
Remaining accrual related to restructuring activities				$ 306	$ 441	1,940	$ 0
2014 Corporate Restructuring | Severance and other employee related costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges						4,100
2014 Corporate Restructuring | Facility related charges
Restructuring Cost and Reserve [Line Items]
Restructuring charges						1,800
2014 Corporate Restructuring | Other Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring charges						$ 181
[1]	Stock-based compensation included in:Cost of revenues – products$280 $315 $331Cost of revenues – services108 120 126Research and development6,489 6,625 6,843Sales and marketing5,944 4,730 5,624General and administrative5,886 7,186 3,595

Restructuring Costs - Schedule

Restructuring Costs - Schedule of Activities Related to Restructuring Plans (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restructuring Reserve
Accrual at beginning of period		$ 441	$ 2,523	$ 1,507
(Credits) charges	[1]	(130)	(517)	10,310
Payments		317	(1,459)	(9,288)
Non-cash items		(133)	(106)	(6)
Accrual at end of period		495	441	2,523
Restructuring Prior to 2014
Restructuring Reserve
Accrual at beginning of period		0	246	1,507
(Credits) charges		0	0	136
Payments		0	(140)	(1,391)
Non-cash items		0	(106)	(6)
Accrual at end of period		0	0	246
Net Optics Restructuring
Restructuring Reserve
Accrual at beginning of period		0	337	0
(Credits) charges		0	(322)	3,852
Payments		0	(15)	(3,515)
Non-cash items		0	0	0
Accrual at end of period		0	0	337
2014 Corporate Restructuring
Restructuring Reserve
Accrual at beginning of period		441	1,940	0
(Credits) charges		(319)	(195)	6,322
Payments		317	(1,304)	(4,382)
Non-cash items		(133)	0	0
Accrual at end of period		306	441	1,940
Other Restructuring
Restructuring Reserve
Accrual at beginning of period		0	0	0
(Credits) charges		189	0	0
Payments		0	0	0
Non-cash items		0	0	0
Accrual at end of period		$ 189	$ 0	$ 0
[1]	Stock-based compensation included in:Cost of revenues – products$280 $315 $331Cost of revenues – services108 120 126Research and development6,489 6,625 6,843Sales and marketing5,944 4,730 5,624General and administrative5,886 7,186 3,595

Concentrations - Narrative (Det

Concentrations - Narrative (Details)	Dec. 31, 2016product_line
Risks and Uncertainties [Abstract]
Number of product lines	2

Concentrations - Schedule of Re

Concentrations - Schedule of Revenue by Product Line (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting, Revenue Reconciling Item [Line Items]
Total	$ 128,163	$ 123,911	$ 120,098	$ 112,673	$ 138,478	$ 125,887	$ 131,610	$ 120,962	$ 484,845	$ 516,937	$ 464,458
Network Test Solutions
Segment Reporting, Revenue Reconciling Item [Line Items]
Total									349,557	386,614	345,673
Network Visibility Solutions
Segment Reporting, Revenue Reconciling Item [Line Items]
Total									$ 135,288	$ 130,323	$ 118,785

Concentrations - Schedule of Co

Concentrations - Schedule of Concentration of Risk, by Risk Factor (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Total revenues | Geographic Concentration Risk | International revenues
Concentration Risk [Line Items]
Percentage of total revenues	43.60%	38.50%	40.80%

Concentrations - Schedule of Pr

Concentrations - Schedule of Property and Equipment, Net by Geographical Location (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Total	$ 36,666	$ 36,536
United States
Property, Plant and Equipment [Line Items]
Total	22,974	23,654
Romania
Property, Plant and Equipment [Line Items]
Total	6,482	6,542
India
Property, Plant and Equipment [Line Items]
Total	3,385	3,576
Other
Property, Plant and Equipment [Line Items]
Total	$ 3,825	$ 2,764

Selected Balance Sheet Data - S

Selected Balance Sheet Data - Schedule of Activity in the Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts Receivable
Balance at beginning of year	$ 1,107	$ 1,011	$ 840
Additions: charged to costs and expenses	416	525	275
Deductions: write-offs, net of recoveries	(612)	(429)	(104)
Balance at end of year	$ 911	$ 1,107	$ 1,011

Selected Balance Sheet Data -61

Selected Balance Sheet Data - Schedule of Investments in Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 71,294	$ 14,566
Gross Unrealized Gains	32	0
Gross Unrealized Losses	(75)	(62)
Fair Value	71,251	14,504
Available-for-sale – short-term | U.S. Treasury, government, and agency debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	37,002	4,301
Gross Unrealized Gains	24	0
Gross Unrealized Losses	(21)	(13)
Fair Value	37,005	4,288
Available-for-sale – short-term | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	34,292	10,265
Gross Unrealized Gains	8	0
Gross Unrealized Losses	(54)	(49)
Fair Value	$ 34,246	$ 10,216

Selected Balance Sheet Data -62

Selected Balance Sheet Data - Schedule of Amortized Cost and Fair Value of Investments (Details) $ in Thousands	Dec. 31, 2016USD ($)
Amortized Cost
Due in less than 1 year	$ 34,715
Due within 1-2 years	20,928
Due within 2-5 years	10,051
Due after 5 years	5,600
Total	71,294
Fair Value
Due in less than 1 year	34,706
Due within 1-2 years	20,928
Due within 2-5 years	10,017
Due after 5 years	5,600
Total	$ 71,251

Selected Balance Sheet Data -63

Selected Balance Sheet Data - Schedule of Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Raw materials	$ 1,252	$ 3,864
Work in process	6,581	11,253
Finished goods	20,824	18,172
Total	$ 28,657	$ 33,289

Selected Balance Sheet Data -64

Selected Balance Sheet Data - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 158,658	$ 145,476
Accumulated depreciation	(121,992)	(108,940)
Total	$ 36,666	36,536
Minimum
Property, Plant and Equipment [Line Items]
Useful Life	3 years
Maximum
Property, Plant and Equipment [Line Items]
Useful Life	5 years
Development equipment
Property, Plant and Equipment [Line Items]
Useful Life	5 years
Property, plant and equipment, gross	$ 39,312	35,831
Demonstration equipment
Property, Plant and Equipment [Line Items]
Useful Life	2 years
Property, plant and equipment, gross	$ 32,543	29,258
Furniture and other equipment
Property, Plant and Equipment [Line Items]
Useful Life	5 years
Property, plant and equipment, gross	$ 23,497	22,066
Computer software
Property, Plant and Equipment [Line Items]
Useful Life	5 years
Property, plant and equipment, gross	$ 22,803	20,702
Computer software | Minimum
Property, Plant and Equipment [Line Items]
Useful Life	3 years
Computer software | Maximum
Property, Plant and Equipment [Line Items]
Useful Life	5 years
Building and leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 22,574	20,921
Building and leasehold improvements | Minimum
Property, Plant and Equipment [Line Items]
Useful Life	1 year
Building and leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Useful Life	40 years
Computer equipment
Property, Plant and Equipment [Line Items]
Useful Life	3 years
Property, plant and equipment, gross	$ 17,929	$ 16,698

Selected Balance Sheet Data -65

Selected Balance Sheet Data - Schedule of Accrued Expenses and Other (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Compensation and related expenses	$ 12,428	$ 12,805
Vacation	5,724	7,967
Commissions	4,711	5,083
Professional fees	3,409	2,163
Other taxes	2,651	3,106
Bonuses	2,202	20,423
Legal contingencies	750	4,825
Income taxes	707	3,599
Other	6,820	10,058
Total	$ 39,402	$ 70,029

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets Carried at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 71,251	$ 14,504
Total financial assets	79,963	14,788
Money market funds | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	769	284
U.S. Treasury, government and agency debt securities | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	37,005	4,288
Corporate debt securities | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	7,943	0
Corporate debt securities | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	34,246	10,216
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	769	284
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	769	284
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury, government and agency debt securities | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate debt securities | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate debt securities | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	79,194	14,504
Significant Other Observable Inputs (Level 2) | Money market funds | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Significant Other Observable Inputs (Level 2) | U.S. Treasury, government and agency debt securities | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	37,005	4,288
Significant Other Observable Inputs (Level 2) | Corporate debt securities | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	7,943	0
Significant Other Observable Inputs (Level 2) | Corporate debt securities | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	34,246	10,216
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	0	0
Significant Unobservable Inputs (Level 3) | Money market funds | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Significant Unobservable Inputs (Level 3) | U.S. Treasury, government and agency debt securities | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Significant Unobservable Inputs (Level 3) | Corporate debt securities | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Significant Unobservable Inputs (Level 3) | Corporate debt securities | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 0	$ 0

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Carrying value
Debt Instrument [Line Items]
Carrying value of Term Loan	$ 35	$ 38.5

Goodwill and Other Intangible68

Goodwill and Other Intangible Assets - Schedule of Purchased Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross	$ 313,631	$ 312,515
Accumulated Amortization	(247,954)	(208,855)
Net	$ 65,677	$ 103,660
Technology
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life	5 years 6 months	5 years 6 months
Gross	$ 185,665	$ 185,665
Accumulated Amortization	(151,672)	(129,509)
Net	$ 33,993	$ 56,156
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life	6 years	6 years
Gross	$ 71,700	$ 71,700
Accumulated Amortization	(59,659)	(51,533)
Net	$ 12,041	$ 20,167
Service agreements
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life	6 years 146 days	6 years 146 days
Gross	$ 30,100	$ 30,100
Accumulated Amortization	(17,968)	(13,272)
Net	$ 12,132	$ 16,828
Trademark
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life	5 years 36 days	5 years 36 days
Gross	$ 11,300	$ 11,300
Accumulated Amortization	(8,966)	(7,000)
Net	$ 2,334	$ 4,300
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life	4 years	4 years
Gross	$ 8,000	$ 8,000
Accumulated Amortization	(7,142)	(5,641)
Net	$ 858	$ 2,359
Other
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life	4 years 8 months	4 years 6 months
Gross	$ 6,866	$ 5,750
Accumulated Amortization	(2,547)	(1,900)
Net	$ 4,319	$ 3,850

Goodwill and Other Intangible69

Goodwill and Other Intangible Assets - Schedule of Estimated Future Amortization Expense (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
2,017	$ 31,930
2,018	20,666
2,019	7,434
2,020	3,892
2,021	700
Thereafter	1,055
Net	$ 65,677	$ 103,660

Income Taxes - Components of In

Income Taxes - Components of Income Before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
U.S.									$ (13,895)	$ (5,307)	$ (53,850)
Foreign									30,684	19,650	1,153
Income (loss) before income taxes	$ 6,949	$ 6,560	$ 8,249	$ (4,969)	$ 12,309	$ 506	$ 6,574	$ (5,046)	$ 16,789	$ 14,343	$ (52,697)

Income Taxes - Schedule of Inco

Income Taxes - Schedule of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current:
Federal	$ 7,260	$ 10,150	$ (372)
State	684	1,635	1,111
Foreign	5,560	4,273	2,538
Deferred:
Federal	25,981	(5,145)	(12,479)
State	11,299	(1,044)	(1,916)
Foreign	(84)	(1,477)	13
Income tax expense (benefit)	$ 50,700	$ 8,392	$ (11,105)

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Federal statutory income tax rate		35.00%
Income Tax Examination [Line Items]
Deferred tax assets			$ 33,057,000
Valuation allowance	$ 45,000,000	$ 45,000,000	2,056,000
Decrease in valuation allowance	(42,900,000)	42,900,000	2,300,000	$ 214,000
Section 382 limitation	700,000	700,000
Undistributed earnings of foreign subsidiaries	124,400,000	124,400,000	100,500,000
Gross unrecognized tax benefits	23,526,000	23,526,000	21,178,000	19,134,000		$ 16,766,000
Unrecognized tax benefits that would affect effective tax rate if recognized	6,600,000	6,600,000
Interest recognized, net of federal benefit		0	2,000	$ 13,000
Accrued interest, net of federal benefit	182,000	182,000	182,000
Other Assets
Income Tax Examination [Line Items]
Deferred tax assets	1,300,000	1,300,000
Long-term deferred tax assets			18,900,000
Prepaid Expenses and Other Current Assets
Income Tax Examination [Line Items]
Current deferred tax assets			14,500,000
Other Liabilities
Income Tax Examination [Line Items]
Long-term deferred tax liabilities	6,200,000	6,200,000	$ 400,000
Domestic Tax Authority
Income Tax Examination [Line Items]
Valuation allowance	44,000,000	44,000,000
Credit carryforwards	20,200,000	20,200,000
Net operating loss carryforwards	9,900,000	9,900,000
Foreign Tax Authority
Income Tax Examination [Line Items]
Valuation allowance	1,000,000	1,000,000
State and Local Jurisdiction
Income Tax Examination [Line Items]
Credit carryforwards	19,400,000	19,400,000
Net operating loss carryforwards	$ 2,000,000	$ 2,000,000
Capital loss carryforwards
Income Tax Examination [Line Items]
Valuation allowance					$ 1,100,000

Income Taxes - Schedule of Net

Income Taxes - Schedule of Net Effective Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Federal statutory expense	$ 5,876	$ 5,020	$ (18,445)
State taxes, net of federal benefit	11,866	269	(805)
Research and development credits	(1,603)	(1,177)	(1,585)
Domestic production deduction	(236)	(595)	0
Foreign branch losses	(2)	90	(1,213)
Stock-based compensation	1,507	1,740	1,700
Foreign rate differential	(5,463)	(3,240)	1,633
Inter-company royalty	2,964	3,121	3,168
Inter-company transfer	1,994	1,994	1,841
Valuation allowance	31,077	(1,939)	0
Unrecognized tax benefits	1,157	1,160	1,497
Other	1,563	1,949	1,104
Income tax expense (benefit)	$ 50,700	$ 8,392	$ (11,105)
Net effective income tax rate	302.00%	58.50%	21.10%

Income Taxes - Primary Componen

Income Taxes - Primary Components of Temporary Differences (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Research and development credit carryforward	$ 13,734	$ 13,544
Deferred revenue	6,272	3,611
Stock-based compensation	11,474	10,674
Inventory adjustments	6,651	8,862
Net operating loss carryforward	4,331	4,939
Realized loss on investments	1,069	3,421
Accrued liabilities and other	1,117	1,056
Depreciation and amortization	5,894	958
Allowance for doubtful accounts	228	282
Deferred tax assets, gross	50,770	47,347
Valuation allowance	(45,000)	(2,056)
Deferred tax assets, net of valuation allowance	5,770	45,291
Deferred tax liabilities:
Depreciation and amortization	(202)	(382)
Intercompany royalty	(10,537)	(11,852)
Net deferred tax liabilities	$ 4,969
Net deferred tax assets		$ 33,057

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns
Unrecognized tax benefits - beginning balance	$ 21,178	$ 19,134	$ 16,766
Gross increases – tax positions taken in prior period	50	188	417
Gross decreases – tax positions taken in prior period	(51)	(161)	(74)
Gross increases – tax positions taken in current period	2,515	2,017	2,167
Lapse of statute of limitations	(166)	0	(142)
Unrecognized tax benefits – ending balance	$ 23,526	$ 21,178	$ 19,134

Commitments and Contingencies -

Commitments and Contingencies - Schedule of Future Minimum Commitments Under Leases (Details) $ in Thousands	Dec. 31, 2016USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,017	$ 11,849
2,018	11,161
2,019	9,496
2,020	8,029
2,021	5,290
Thereafter	8,282
Total	54,107
Minimum sublease rentals	$ 43

Commitments and Contingencies77

Commitments and Contingencies - Narrative (Details) - USD ($)	Feb. 09, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Nov. 17, 2015
Commitments and Contingencies Disclosure [Abstract]
Rent expense			$ 9,500,000	$ 8,900,000	$ 13,700,000
Class Action Settlement Agreement | Pending Litigation
Loss Contingencies [Line Items]
Settlement payment		$ 3,500,000
Attorney's fees and expenses | Derivative Action Settlement Agreement | Pending Litigation
Loss Contingencies [Line Items]
Attorneys' fees and expenses and accrued liability						$ 575,000
Unfavorable Regulatory Action | SEC Investigation | Pending Litigation
Loss Contingencies [Line Items]
Attorneys' fees and expenses and accrued liability			750,000
Contingent civil penalty			$ 750,000
Subsequent Event | Unfavorable Regulatory Action | SEC Investigation | Settled Litigation
Loss Contingencies [Line Items]
Payment made to SEC	$ 750,000

Shareholders_ Equity - Second A

Shareholders’ Equity - Second Amended and Restated Ixia 2008 Equity Incentive Plan (Narrative) (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2008
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant-date fair value (in dollars per share)		$ 3.44	$ 4.21	$ 3.36
Intrinsic value of options exercised		$ 3,100,000	$ 2,300,000	$ 1,100,000
Weighted average period for recognition		1 year 4 months 17 days
Expense recognition period of RSUs		1 year 4 months 28 days
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of RSU's vested (in dollars per share)		$ 8,000,000	$ 9,100,000	$ 7,400,000
2008 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period					7 years
Grant price as a (percent)					100.00%
Voting shares (as a percent)					10.00%
Award vesting period					4 years
Increase in number of shares available for future grants (in shares)	9,800,000
Number of shares authorized (in shares)		29,000,000
Number of shares available for future grant (in shares)		6,100,000
2008 Plan | Non-employee director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value limit on total number of shares	$ 500,000
2008 Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise period					90 days
2008 Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise period					180 days
2008 Plan | ISOs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant price as a (percent)					110.00%
2008 Plan | Subject to options and share appreciation rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limit on total number of shares (in shares)	1,000,000
2008 Plan | Subject to RSUs and restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limit on total number of shares (in shares)	1,000,000
2008 Plan | Subject to cash awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value limit on total number of shares	$ 2,000,000

Shareholders_ Equity - Summary

Shareholders’ Equity - Summary of Stock Option Activity (Details) - Options - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Number of Options
Balance at beginning of period (in shares)	5,474
Granted (in shares)	1,240
Exercised (in shares)	(775)
Forfeited/canceled (in shares)	(459)
Balance at end of period (in shares)	5,480	5,474
Vested and expected to vest at end of period (in shares)	5,336
Exercisable at end of period (in shares)	3,395
Weighted Average Exercise Price Per Share
Balance at beginning of period (in dollars per share)	$ 12.11
Granted (in dollars per share)	11.30
Exercised (in dollars per share)	8.68
Forfeited/canceled (in dollars per share)	14.56
Balance at end of period (in dollars per share)	12.21	$ 12.11
Vested and expected to vest at end of period (in dollars per share)	12.23
Exercisable at end of period (in dollars per share)	$ 12.96
Weighted Average Remaining Contractual Life (in years)
Outstanding (term)	4 years 4 months 4 days	4 years 4 months 6 days
Vested and expected to vest (term)	4 years 3 months 18 days
Exercisable (term)	3 years 6 months 21 days
Aggregate Intrinsic Value
Outstanding	$ 22,638	$ 9,350
Vested and expected to vest	21,933
Exercisable	$ 11,950

Shareholders_ Equity - Summar80

Shareholders’ Equity - Summary of RSU Activity (Details) - RSUs shares in Thousands	12 Months Ended
	Dec. 31, 2016$ / sharesshares
Number of Awards
Balance at beginning of period (in shares) | shares	1,963
Awarded (in shares) | shares	1,114
Vested (in shares) | shares	(730)
Forfeited/canceled (in shares) | shares	(188)
Balance at end of period (in shares) | shares	2,159
Weighted Average Grant Date Fair Value Per Share
Balance at beginning of period (in dollars per share) | $ / shares	$ 12.63
Awarded (in dollars per share) | $ / shares	11.70
Vested (in dollars per share) | $ / shares	13.10
Forfeited/canceled (in dollars per share) | $ / shares	12.13
Balance at end of period (in dollars per share) | $ / shares	$ 12.03

Shareholders_ Equity - Employee

Shareholders’ Equity - Employee Stock Purchase Plan (Narrative) (Details)	Feb. 23, 2016	Dec. 31, 2016shares	Dec. 31, 2015shares	Dec. 31, 2014shares	Dec. 31, 2010USD ($)purchase_periodshares	Jun. 30, 2016shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of purchase periods | purchase_period					4
Share repurchase program, term	12 months				10 years
Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payroll deduction (as a percent)					20.00%
Payroll deduction | $					$ 21,250
Length of offering period					24 months
Purchase period					6 months
Percentage of purchase price per share					85.00%
Increase in number of shares available for future grants (in shares)					500,000	500,000
Number of shares authorized (in shares)		5,300,000
Number of shares available for future grant (in shares)		965,000
Stock issued issued under the Purchase Plan (in shares)		1,026,000	988,000	685,000

Shareholders_ Equity - Schedule

Shareholders’ Equity - Schedule of Weighted Average Assumptions Used to Calculate Estimated Fair Value (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected lives	4 years	3 years 10 months 24 days	4 years
Risk-free interest rates	1.10%	1.20%	1.20%
Dividend yield (as a percent)	0.00%	0.00%	0.00%
Expected volatility (as a percent)	37.40%	43.30%	46.70%
Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected lives	1 year 3 months	1 year 3 months	1 year 2 months
Risk-free interest rates	0.60%	0.40%	0.20%
Dividend yield (as a percent)	0.00%	0.00%	0.00%
Expected volatility (as a percent)	35.70%	28.40%	32.90%

Shareholders_ Equity - Schedu83

Shareholders’ Equity - Schedule Stock-Based Compensation by Award Type (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 18,707	$ 18,976	$ 16,519
Options
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	4,438	5,032	3,934
RSUs
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	11,267	10,078	9,328
Common shares issued under the Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 3,002	$ 3,866	$ 3,257

Shareholders_ Equity - Stock-Ba

Shareholders’ Equity - Stock-Based Compensation Expense (Narrative) (Details) $ in Millions	Dec. 31, 2016USD ($)
Unvested options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Gross unrecognized stock-based compensation	$ 3.9
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Gross unrecognized stock-based compensation	11.8
Common shares issued under the Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Gross unrecognized stock-based compensation	$ 4

Shareholders_ Equity - Summar85

Shareholders’ Equity - Summary of Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Balance at beginning of period	$ 519,011	$ 481,091	$ 499,112
Other comprehensive (loss) gain before reclassifications	138	(260)
Amounts reclassified from accumulated other comprehensive loss	(13)	20
Other comprehensive income (loss)	125	(240)	(416)
Balance at end of period	511,537	519,011	481,091
Unrealized Gains and Losses on Available-for- Sale Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Balance at beginning of period	(88)	(32)
Other comprehensive (loss) gain before reclassifications	75	(76)
Amounts reclassified from accumulated other comprehensive loss	(13)	20
Other comprehensive income (loss)	62	(56)
Balance at end of period	(26)	(88)	(32)
Foreign Currency Items
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Balance at beginning of period	(945)	(761)
Other comprehensive (loss) gain before reclassifications	63	(184)
Amounts reclassified from accumulated other comprehensive loss	0	0
Other comprehensive income (loss)	63	(184)
Balance at end of period	(882)	(945)	(761)
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Balance at beginning of period	(1,033)	(793)	(377)
Balance at end of period	$ (908)	$ (1,033)	$ (793)

Shareholders_ Equity - Other Co

Shareholders’ Equity - Other Comprehensive Income (Loss) (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Equity [Abstract]
Gross reclassification from accumulated other comprehensive loss for realized gains (losses)	$ 13	$ (20)
Gross unrealized gains (losses)	$ 118	$ (125)

Shareholders_ Equity - Stock Bu

Shareholders’ Equity - Stock Buyback Program (Narrative) (Details) - USD ($)	Feb. 23, 2016	Dec. 31, 2016	Dec. 31, 2010
Equity [Abstract]
Share repurchase program, term	12 months		10 years
Share repurchase program, approved amount	$ 25,000,000
Shares repurchased (in shares)		707,332
Value of shares repurchased		$ 6,900,000
Remaining amount available for share repurchases		$ 18,100,000

Retirement Plan (Details)

Retirement Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Matching contribution (as a percent)	50.00%
Maximum annual contributions (up to)	$ 2,500
Employer contribution amount	$ 2,900,000	$ 3,000,000	$ 1,600,000

Earnings Per Share - Computatio

Earnings Per Share - Computation of Basic and Diluted Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Basic Presentation:
Net (loss) income	$ (37,520)	$ 4,773	$ 1,523	$ (2,687)	$ 5,751	$ 4,008	$ 5,803	$ (9,611)	$ (33,911)	$ 5,951	$ (41,592)
Weighted average common shares outstanding (in shares)									81,470	79,633	77,629
Basic (loss) earnings per share (in dollars per share)	$ (0.46)	$ 0.06	$ 0.02	$ (0.03)	$ 0.07	$ 0.05	$ 0.07	$ (0.12)	$ (0.42)	$ 0.07	$ (0.54)
Diluted presentation:
Net (loss) income	$ (37,520)	$ 4,773	$ 1,523	$ (2,687)	$ 5,751	$ 4,008	$ 5,803	$ (9,611)	$ (33,911)	$ 5,951	$ (41,592)
Weighted average common shares outstanding (in shares)									81,470	79,633	77,629
Effect of dilutive securities:
Stock options and other share-based awards (in shares)									0	1,826	0
Dilutive potential common shares (in shares)									81,470	81,459	77,629
Diluted (loss) earnings per share (in dollars per share)	$ (0.46)	$ 0.06	$ 0.02	$ (0.03)	$ 0.07	$ 0.05	$ 0.07	$ (0.12)	$ (0.42)	$ 0.07	$ (0.54)

Earnings Per Share - Narrative

Earnings Per Share - Narrative (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee stock options and other share-based awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	4.7	2.6	4.7
Convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)		8.4	10.3

Quarterly Financial Summary (91

Quarterly Financial Summary (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Total revenues		$ 128,163	$ 123,911	$ 120,098	$ 112,673	$ 138,478	$ 125,887	$ 131,610	$ 120,962	$ 484,845	$ 516,937	$ 464,458
Total cost of revenues		33,558	33,352	30,343	31,660	35,697	33,913	34,983	35,001
Gross profit		94,605	90,559	89,755	81,013	102,781	91,974	96,627	85,961
Income (loss) before income taxes		6,949	6,560	8,249	(4,969)	12,309	506	6,574	(5,046)	16,789	14,343	(52,697)
Net (loss) income		$ (37,520)	$ 4,773	$ 1,523	$ (2,687)	$ 5,751	$ 4,008	$ 5,803	$ (9,611)	$ (33,911)	$ 5,951	$ (41,592)
(Loss) earnings per share:
Basic (in dollars per share)		$ (0.46)	$ 0.06	$ 0.02	$ (0.03)	$ 0.07	$ 0.05	$ 0.07	$ (0.12)	$ (0.42)	$ 0.07	$ (0.54)
Diluted (in dollars per share)		$ (0.46)	$ 0.06	$ 0.02	$ (0.03)	$ 0.07	$ 0.05	$ 0.07	$ (0.12)	$ (0.42)	$ 0.07	$ (0.54)
Interim Period, Costs Not Allocable [Line Items]
Amortization of intangible assets	[1]									$ 39,099	$ 42,315	$ 46,901
Valuation allowance established against remaining net deferred tax assets		$ 42,900								$ (42,900)	$ (2,300)	$ (214)
Cost of revenues
Interim Period, Costs Not Allocable [Line Items]
Amortization of intangible assets		$ 6,200	$ 6,300	$ 6,400	$ 6,400	$ 6,400	$ 6,400	$ 6,400	$ 6,400
[1]	Stock-based compensation included in:Cost of revenues – products$280 $315 $331Cost of revenues – services108 120 126Research and development6,489 6,625 6,843Sales and marketing5,944 4,730 5,624General and administrative5,886 7,186 3,595

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Oct. 31, 2017
Business Acquisition [Line Items]
Incurred costs related to the Merger	[1]	$ 785	$ 656	$ 3,277
Keysight
Business Acquisition [Line Items]
Incurred costs related to the Merger		$ 802
Scenario, Forecast | Subsequent Event | Keysight | Keysight
Business Acquisition [Line Items]
Right to receive cash per share at the effective time (in dollars per share)					$ 19.65
Scenario, Forecast | Subsequent Event | Termination of merger agreement | Keysight
Business Acquisition [Line Items]
Contingent termination fee					$ 59,700
Scenario, Forecast | Subsequent Event | Failure to close on effective date | Keysight | Keysight
Business Acquisition [Line Items]
Contingent termination fee					$ 500,000
[1]	Stock-based compensation included in:Cost of revenues – products$280 $315 $331Cost of revenues – services108 120 126Research and development6,489 6,625 6,843Sales and marketing5,944 4,730 5,624General and administrative5,886 7,186 3,595