InterDigital (IDCC) 10-K 22 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information Document - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 20, 2018	Jun. 30, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	INTERDIGITAL, INC.
Entity Central Index Key	1,405,495
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		34,627,324
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 2,654,386,865

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
CURRENT ASSETS:
Cash and cash equivalents	$ 433,014	$ 404,074
Short-term Investments	724,981	548,687
Accounts Receivable, Net	216,293	228,464
Prepaid and other current assets	21,506	39,894
Total current assets	1,395,794	1,221,119
NON-CURRENT ASSETS:
PROPERTY AND EQUIPMENT, NET	10,673	12,626
PATENTS, NET	325,408	310,768
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent	84,582	149,532
OTHER NON-CURRENT ASSETS, NET	37,963	33,808
Total non-current assets	458,626	506,734
TOTAL ASSETS	1,854,420	1,727,853
CURRENT LIABILITIES:
Long-term Debt, Current Maturities	0	0
Accounts payable	10,260	14,050
Accrued compensation and related expenses	24,571	22,065
Deferred revenue	307,142	360,192
Taxes Payable	14,881	10,660
Dividends Payable	12,156	10,290
Other accrued expenses	7,431	8,223
Total current liabilities	376,441	425,480
LONG-TERM DEBT	285,126	272,021
NON-CURRENT LIABILITIES
LONG-TERM DEFERRED REVENUE	309,671	261,013
OTHER LONG-TERM LIABILITIES	10,034	14,971
TOTAL LIABILITIES	981,272	973,485
COMMITMENTS AND CONTINGENCIES
SHAREHOLDERS’ EQUITY:
Preferred Stock, $0.10 par value, 0 and 14,399 shares authorized 0 shares issued and outstanding	0	0
Common Stock, $0.01 par value, 100,000 shares authorized, 68,968 and 68,602 shares issued and 45,398 and 45,032 shares outstanding	707	703
Additional paid-in capital	680,040	683,549
Retained earnings	1,249,091	1,120,766
Accumulated other comprehensive income	(2,083)	(514)
Stockholders' Equity before Treasury Stock	1,927,755	1,804,504
Treasury stock, 23,570 shares of common held at cost	1,072,488	1,064,795
Total shareholders’ equity	855,267	739,709
Noncontrolling Interest in Variable Interest Entity	17,881	14,659
Total equity	873,148	754,368
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	$ 1,854,420	$ 1,727,853

Consolidated Statements of Inco

Consolidated Statements of Income Statement - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
REVENUES
Technology Services Revenue	$ 20,580	$ 10,494	$ 8,947
Revenues	532,938	665,854	441,435
REVENUES	512,358	655,360	432,488
OPERATING EXPENSES:
Patent administration and licensing	111,157	113,544	120,401
Development Expense	70,708	68,733	72,702
Selling, general and administrative	49,578	46,271	39,783
Total Operating Expenses	231,443	228,548	232,886
Income from operations	301,495	437,306	208,549
OTHER INCOME:
Other Nonoperating Income (Expense)	(9,105)	(15,035)	(27,534)
Income before income taxes	292,390	422,271	181,015
INCOME TAX PROVISION	(121,676)	(116,791)	(64,621)
NET INCOME	170,714	305,480	116,394
Net Income (Loss) Attributable to Noncontrolling Interest	(3,579)	(3,521)	(2,831)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 174,293	$ 309,001	$ 119,225
NET INCOME PER COMMON SHARE — BASIC	$ 5.04	$ 8.95	$ 3.31
WEIGHTED AVERAGE NUMBER OF COMMON SHARES OUTSTANDING — BASIC	34,605	34,526	36,048
NET INCOME PER COMMON SHARE — DILUTED	$ 4.87	$ 8.78	$ 3.27
WEIGHTED AVERAGE NUMBER OF COMMON SHARES OUTSTANDING — DILUTED	35,779	35,189	36,463
Common Stock, Dividends, Per Share, Declared	$ 1.30	$ 1	$ 0.80

Consolidated Statements of Cash

Consolidated Statements of Cash Flows Statement - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accrued Capitalized Patent Costs		$ 146	$ 18,155
NET INCOME	$ 170,714	305,480	116,394
Multiple Element Arrangements [Abstract] [Abstract]
Net cash provided by operating activities	315,800	434,159	124,348
Depreciation, Depletion and Amortization	57,053	52,753	47,793
Amortization of Financing Costs and Discounts	13,105	15,252	20,869
Recognition of Deferred Revenue	(394,747)	(321,313)	(163,354)
Increase in deferred revenue	357,855	527,034	113,962
Increase (Decrease) in Deferred Income Taxes	64,950	13,261	(34,770)
Share-based Compensation	18,062	21,840	15,139
Other than Temporary Impairment Losses, Investments		200
Gain (Loss) on Disposition of Assets	0	(3,351)	0
Other Operating Activities, Cash Flow Statement	(2)	(32)	436
Decrease (increase) in assets:
Increase (Decrease) in Receivables	12,171	(169,927)	(2,166)
Deferred charges and other current assets	19,426	(15,222)	8,489
Increase (decrease) in liabilities:
Increase (Decrease) in Accounts Payable	(3,789)	(5,564)	2,503
Accrued taxes payable	4,220	8,793	1,501
Other accrued expenses	(3,218)	5,155	(2,448)
Net Cash Provided by (Used in) Investing Activities [Abstract]
Purchases of short-term investments	930,016	560,075	643,087
Sales of short-term investments	751,308	434,510	495,201
Purchases of property and equipment	2,071	5,882	3,700
Capitalized patent costs	34,933	32,658	29,766
Payments to Acquire Intangible Assets	0	4,900	20,000
Payments to Acquire Businesses, Net of Cash Acquired	0	(48,000)	0
Payments for (Proceeds from) Long-term Investments	(4,585)	(2,000)	(12,623)
Net cash used in investing activities	(220,297)	(219,005)	(213,975)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net proceeds from exercise of stock options	382	485	46
Proceeds from Convertible Debt	0	0	316,000
Repayments of Long-term Debt	0	(230,000)	0
Proceeds from (Payments for) Other Financing Activities	0	0	(59,376)
Proceeds from Hedge, Financing Activities	0	0	4,500
Dividends paid	43,255	31,135	28,937
Payments Related to Tax Withholding for Share-based Compensation	(22,798)	(3,381)	(9,849)
Proceeds from Issuance of Warrants	0	0	42,881
Payments of debt issuance costs	0	0	(9,403)
Proceeds from Noncontrolling Interests	6,801	6,804	9,358
Excess Tax Benefit from Share-based Compensation, Financing Activities	0	625	2,457
Payments for Repurchase of Common Stock	7,693	64,685	96,410
Net Cash Provided by (Used in) Financing Activities	(66,563)	(321,287)	171,267
Cash and Cash Equivalents, Period Increase (Decrease)	28,940	(106,133)	81,640
CASH AND CASH EQUIVALENTS, END OF PERIOD	433,014	404,074	510,207
Interest Paid	4,740	7,615	7,988
Income taxes paid, including foreign witholding taxes	66,793	108,635	85,780
Dividends Payable	12,156	10,290	7,068
Other Significant Noncash Transaction, Value of Consideration Received	32,500	$ 7,900	$ 24,123
Patents [Member]
Accrued Capitalized Patent Costs	$ (1)

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	$ (1,569)	$ (336)	$ (296)
Net Income (Loss) Attributable to Parent	170,714	305,480	116,394
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	174,293	309,001	119,225
Total Comprehensive Income	169,145	305,144	116,098
Net Income (Loss) Attributable to Noncontrolling Interest	(3,579)	(3,521)	(2,831)
Total comprehensive income attributable to InterDigital, Inc.	$ 172,724	$ 308,665	$ 118,929

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Treasury Stock [Member]	Noncontrolling Interest [Member]
Noncontrolling Interest in Variable Interest Entity							$ 7,349
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 119,225
Beginning balance at Dec. 31, 2014	475,677	$ 698	$ 614,162	$ 757,050	$ 118	$ (903,700)
Beginning balance in Shares at Dec. 31, 2014		69,800
Beginning balance Treasury Stock, Shares at Dec. 31, 2014						32,880
NET INCOME	116,394
Other Comprehensive Income (Loss), Net of Tax	(296)
Proceeds from Noncontrolling Interests	9,358						9,358
Distribution preference	(2,500)
Net Income (Loss) Attributable to Noncontrolling Interest	(2,831)						(2,831)
Total Comprehensive Income	116,098
Dividends	28,548		(694)	29,242
Exercise of Common Stock options, shares		5
Exercise of Common Stock options	(46)		(46)
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures		325
Issuance of Restricted Common Stock, net value	9,846	$ (3)	9,849
Tax benefit from exercise of stock options	2,457		2,457
Amortization of unearned compensation			15,139
Payments of Financing Costs	(2,430)
Treasury Stock, Shares, Acquired						1,836
Convertible note hedge transactions, net of tax	(38,594)
Issuance of Warrants during period	42,881
Treasury Stock, Value, Acquired, Cost Method						$ 96,410
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt	38,567
Ending balance at Dec. 31, 2015		$ 701	663,073	847,033	(178)	$ (1,000,110)
Ending balance in Shares at Dec. 31, 2015		70,130
Ending balance Treasury Stock, Shares at Dec. 31, 2015						34,716
Noncontrolling Interest in Variable Interest Entity							11,376
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	521,895
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	309,001
NET INCOME	305,480
Other Comprehensive Income (Loss), Net of Tax	(336)
Proceeds from Noncontrolling Interests	6,804						6,804
Net Income (Loss) Attributable to Noncontrolling Interest	(3,521)						(3,521)
Total Comprehensive Income	305,144
Dividends	34,361		(907)	35,268
Exercise of Common Stock options, shares		51
Exercise of Common Stock options	(486)		(485)
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures		137
Issuance of Restricted Common Stock, net value	(3,380)	$ (1)	(3,381)
Tax benefit from exercise of stock options			625
Amortization of unearned compensation			21,840
Treasury Stock, Shares, Acquired						1,304
Treasury Stock, Value, Acquired, Cost Method						$ (64,685)
Ending balance at Dec. 31, 2016	$ 739,709	$ 703	683,549	1,120,766	(514)	$ (1,064,795)
Ending balance in Shares at Dec. 31, 2016	70,318	70,318
Ending balance Treasury Stock, Shares at Dec. 31, 2016	36,020					36,020
Noncontrolling Interest in Variable Interest Entity	$ 14,659						14,659
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	754,368
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	174,293
NET INCOME	170,714
Other Comprehensive Income (Loss), Net of Tax	(1,569)
Proceeds from Noncontrolling Interests	6,801						6,801
Net Income (Loss) Attributable to Noncontrolling Interest	(3,579)						(3,579)
Total Comprehensive Income	169,145
Dividends	$ 45,122		(846)	45,968
Exercise of Common Stock options, shares	9	9
Exercise of Common Stock options	$ (382)		(381)
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures		422
Issuance of Restricted Common Stock, net value	(22,795)	$ (3)	(22,798)
Amortization of unearned compensation			18,062
Treasury Stock, Shares, Acquired						107
Treasury Stock, Value, Acquired, Cost Method						$ (7,693)
Ending balance at Dec. 31, 2017	$ 855,267	$ 707	$ 680,040	$ 1,249,091	$ (2,083)	$ (1,072,488)
Ending balance in Shares at Dec. 31, 2017	70,749	70,749
Ending balance Treasury Stock, Shares at Dec. 31, 2017	36,127					36,127
Noncontrolling Interest in Variable Interest Entity	$ 17,881						$ 17,881
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 873,148

Background

Background	12 Months Ended
	Dec. 31, 2017
BACKGROUND [Abstract]
Business Description and Basis of Presentation [Text Block]	1. BACKGROUND InterDigital designs and develops advanced technologies that enable and enhance wireless communications and capabilities. Since our founding in 1972, we have designed and developed a wide range of innovations that are used in digital cellular and wireless products and networks, including 2G, 3G, 4G and IEEE 802-related products and networks. We are a leading contributor of innovation to the wireless communications industry.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Summary of Significant Accounting Policies [Abstract]
Summary of Significant Accounting Policies [Text Block]	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Principles of Consolidation The accompanying consolidated financial statements include all of our accounts and all entities in which we have a controlling interest and/or are required to be consolidated in accordance with the Generally Accepted Accounting Principles in the United States (“GAAP”). All significant intercompany accounts and transactions have been eliminated in consolidation. In determining whether we are the primary beneficiary of a variable interest entity and therefore required to consolidate, we apply a qualitative approach that determines whether we have both the power to direct the economically significant activities of the entity and the obligation to absorb losses of, or the right to receive benefits from, the entity that could potentially be significant to that entity. These considerations impact the way we account for our existing collaborative relationships and other arrangements. We continuously assess whether we are the primary beneficiary of a variable interest entity as changes to existing relationships or future transactions may result in us consolidating or deconsolidating our partner(s) to collaborations and other arrangements. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from these estimates. If different assumptions were made or different conditions had existed, our financial results could have been materially different. Cash and Cash Equivalents We classify all highly liquid investment securities with original maturities of three months or less at date of purchase as cash equivalents. Our investments are comprised of mutual and exchange traded funds, commercial paper, United States and municipal government obligations and corporate securities. Management determines the appropriate classification of our investments at the time of acquisition and re-evaluates such determination at each balance sheet date. Cash and cash equivalents at December 31, 2017 and 2016 consisted of the following (in thousands): December 31, 2017 2016 Money market and demand accounts $ 417,348 $ 404,074 Commercial paper 15,666 — $ 433,014 $ 404,074 Marketable Securities At December 31, 2017 and 2016 , all marketable securities have been classified as available-for-sale and are carried at fair value, with unrealized gains and losses reported net-of-tax as a separate component of shareholders’ equity. Substantially all of our investments are investment grade government and corporate debt securities that have maturities of less than 3 years, and we have both the ability and intent to hold the investments until maturity. During both 2016 and 2015, we recorded other-than-temporary impairments of approximately $0.2 million . The gross realized gains and losses on sales of marketable securities were not significant during the years ended December 31, 2017, 2016 and 2015. Marketable securities as of December 31, 2017 and 2016 consisted of the following (in thousands): December 31, 2017 Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Available-for-sale securities Commercial paper 66,132 — — 66,132 U.S. government securities 513,645 — (2,613 ) 511,032 Corporate bonds, asset backed and other securities 164,075 35 (627 ) 163,483 Total available-for-sale securities $ 743,852 $ 35 $ (3,240 ) $ 740,647 Reported in: Cash and cash equivalents $ 15,666 Short-term investments 724,981 Total marketable securities $ 740,647 December 31, 2016 Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Available-for-sale securities Commercial paper 113,490 — — 113,490 U.S. government securities 224,583 9 (262 ) 224,330 Corporate bonds, asset backed and other securities 211,406 28 (567 ) 210,867 Total available-for-sale securities $ 549,479 $ 37 $ (829 ) $ 548,687 Reported in: Cash and cash equivalents $ — Short-term investments 548,687 Total marketable securities $ 548,687 At December 31, 2017 and 2016 , $345.0 million and $404.8 million , respectively, of our short-term investments had contractual maturities within one year. The remaining portions of our short-term investments had contractual maturities primarily within two to five years Concentration of Credit Risk and Fair Value of Financial Instruments Financial instruments that potentially subject us to concentration of credit risk consist primarily of cash equivalents, short-term investments and accounts receivable. We place our cash equivalents and short-term investments only in highly rated financial instruments and in United States government instruments. Our accounts receivable are derived principally from patent license and technology solutions agreements. At December 31, 2017 and 2016, three and four licensees comprised 96% and 91% , respectively, of our accounts receivable balance. We perform ongoing credit evaluations of our licensees, who generally include large, multinational, wireless telecommunications equipment manufacturers. We believe that the book values of our financial instruments approximate their fair values. Fair Value Measurements We use various valuation techniques and assumptions when measuring the fair value of our assets and liabilities. We utilize market data or assumptions that market participants would use in pricing the asset or liability, including assumptions about risk and the risks inherent in the inputs to the valuation technique. This guidance established a hierarchy that prioritizes fair value measurements based on the types of input used for the various valuation techniques (market approach, income approach and cost approach). The levels of the hierarchy are described below: Level 1 Inputs — Level 1 includes financial instruments for which quoted market prices for identical instruments are available in active markets. Level 2 Inputs — Level 2 includes financial instruments for which there are inputs other than quoted prices included within Level 1 that are observable for the instrument such as quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets with insufficient volume or infrequent transactions (less active markets) or model-driven valuations in which significant inputs are observable or can be derived principally from, or corroborated by, observable market data, including market interest rate curves, referenced credit spreads and pre-payment rates. Level 3 Inputs — Level 3 includes financial instruments for which fair value is derived from valuation techniques including pricing models and discounted cash flow models in which one or more significant inputs are unobservable, including the company’s own assumptions. The pricing models incorporate transaction details such as contractual terms, maturity and, in certain instances, timing and amount of future cash flows, as well as assumptions related to liquidity and credit valuation adjustments of marketplace participants. Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of financial assets and financial liabilities and their placement within the fair value hierarchy. We use quoted market prices for similar assets to estimate the fair value of our Level 2 investments. Our financial assets are included within short-term investments on our consolidated balance sheets, unless otherwise indicated. Our financial assets that are accounted for at fair value on a recurring basis are presented in the tables below as of December 31, 2017 and December 31, 2016 (in thousands): Fair Value as of December 31, 2017 Level 1 Level 2 Level 3 Total Assets: Money market and demand accounts (a) $ 417,348 $ — $ — $ 417,348 Commercial paper (b) — 66,132 — 66,132 U.S. government securities — 511,032 — 511,032 Corporate bonds, asset backed and other securities — 163,483 — 163,483 $ 417,348 $ 740,647 $ — $ 1,157,995 _______________ (a) Included within cash and cash equivalents. (b) Includes $15.7 million of commercial paper that is included within cash and cash equivalents. Fair Value as of December 31, 2016 Level 1 Level 2 Level 3 Total Assets: Money market and demand accounts (a) $ 404,074 $ — $ — $ 404,074 Commercial paper — 113,490 — 113,490 U.S. government securities — 224,330 — 224,330 Corporate bonds and asset backed securities — 210,867 — 210,867 $ 404,074 $ 548,687 $ — $ 952,761 _______________ (a) Included within cash and cash equivalents. The principal amount, carrying value and related estimated fair value of the Company's long-term debt reported in the Consolidated Balance Sheets as of December 31, 2017 and December 31, 2016 are as follows (in thousands): December 31, 2017 December 31, 2016 Principal Amount Carrying Value Fair Value Principal Amount Carrying Fair Value Total Long-Term Debt $ 316,000 $ 285,126 $ 377,029 $ 316,000 $ 272,021 $ 428,575 The aggregate fair value of the principal amount of the long-term debt (Level 2 Notes as defined in Note 6 " Obligations ") was calculated using inputs such as actual trade data, benchmark yields, broker/dealer quotes and other similar data, which were obtained from independent pricing vendors, quoted market prices or other sources. As discussed in Note 3, "Significant Agreements," we acquired patents associated with a patent license agreement signed during fourth quarter 2017. We have recorded these patents based on their total estimated fair value of $19.7 million and will amortize them over their estimated useful lives. Additionally, as previously disclosed, during third quarter 2016, we entered into a multi-year, worldwide, non-exclusive, royalty-bearing patent license agreement with Huawei. A portion of the consideration for the agreement was in the form of patents from Huawei. We received the first portion of the patents as of September 30, 2016, and the remaining patents during third quarter 2017. We have recorded these additional patents based on their total estimated fair value of $12.8 million and will amortize them over their estimated useful lives. We estimated the fair value of the patents in these transactions through a combination of a discounted cash flow analysis (the income approach) and an analysis of comparable market transactions (the market approach). For the income approach, the inputs and assumptions used to develop these estimates were based on a market participant perspective and included estimates of projected royalties, discount rates, economic lives and income tax rates, among others. For the market approach, judgment was applied as to which market transactions were most comparable to the transaction. Foreign Currency Translation The functional currency of substantially all of the Company's wholly-owned subsidiaries is the U.S. dollar. Certain subsidiaries have monetary assets and liabilities that are denominated in a currency that is different than the functional currency. The gains and losses resulting from this remeasurement and translation of monetary assets denominated in a currency that is different than the functional currency are reflected in the determination of net income (loss). Property and Equipment Property and equipment are stated at cost. Depreciation and amortization of property and equipment are provided using the straight-line method. The estimated useful lives for computer equipment, computer software, engineering and test equipment and furniture and fixtures are generally three to five years. Leasehold improvements are amortized over the lesser of their estimated useful lives or their respective lease terms, which are generally five to ten years. Buildings are being depreciated over twenty-five years. Expenditures for major improvements and betterments are capitalized, while minor repairs and maintenance are charged to expense as incurred. Leases meeting certain capital lease criteria are capitalized and the net present value of the related lease payments is recorded as a liability. Amortization of capital leased assets is recorded using the straight-line method over the lesser of the estimated useful lives or the lease terms. Upon the retirement or disposition of property, plant and equipment, the related cost and accumulated depreciation or amortization are removed, and a gain or loss is recorded. Internal-Use Software Costs We capitalize costs associated with software developed for internal use that are incurred during the software development stage. Such costs are limited to expenses incurred after management authorizes and commits to a computer software project, believes that it is more likely than not that the project will be completed, the software will be used to perform the intended function with an estimated service life of two years or more, and the completion of conceptual formulation, design and testing of possible software project alternatives (the preliminary design stage). Costs incurred after final acceptance testing has been successfully completed are expensed. Capitalized computer software costs are amortized over their estimated useful life of three years. All computer software costs capitalized to date relate to the purchase, development and implementation of engineering, accounting and other enterprise software. Other-than-Temporary Impairments We review our investment portfolio during each reporting period to determine whether there are identified events or circumstances that would indicate there is a decline in the fair value that is considered to be other-than-temporary. For non-public investments, if there are no identified events or circumstances that would have a significant adverse effect on the fair value of the investment, then the fair value is not estimated. If an investment is deemed to have experienced an other-than-temporary decline below its cost basis, we reduce the carrying amount of the investment to its quoted or estimated fair value, as applicable, and establish a new cost basis for the investment. We charge the impairment to the Other Expense (Net) line of our Consolidated Statements of Income. Investments in Other Entities We may make strategic investments in companies that have developed or are developing technologies that are complementary to our business. We account for our investments using either the cost or equity method of accounting. Under the cost method, we do not adjust our investment balance when the investee reports profit or loss but monitor the investment for an other-than-temporary decline in value. On a quarterly basis, we monitor our investment’s financial position and performance to assess whether there are any triggering events or indicators present that would be indicative of an other-than-temporary impairment of our investment. When assessing whether an other-than-temporary decline in value has occurred, we consider such factors as the valuation placed on the investee in subsequent rounds of financing, the performance of the investee relative to its own performance targets and business plan, and the investee’s revenue and cost trends, liquidity and cash position, including its cash burn rate, and updated forecasts. Under the equity method of accounting, we initially record our investment in the stock of an investee at cost, and adjust the carrying amount of the investment to recognize our share of the earnings or losses of the investee after the date of acquisition. The amount of the adjustment is included in the determination of net income, and such amount reflects adjustments similar to those made in preparing consolidated statements including adjustments to eliminate intercompany gains and losses, and to amortize, if appropriate, any difference between our cost and underlying equity in net assets of the investee at the date of investment. The investment is also adjusted to reflect our share of changes in the investee’s capital. Dividends received from an investee reduce the carrying amount of the investment. When there are a series of operating losses by the investee or when other factors indicate that a decrease in value of the investment has occurred which is other than temporary, we recognize an impairment equal to the difference between the fair value and the carrying amount of our investment. The carrying costs of our investments are included within Other Non-Current Assets on our Consolidated Balance Sheets. During 2017 and 2016, we made investments in other entities for $4.6 million , and $2.0 million , respectively. Due to the fact that we do not have significant influence over any of these entities, we are accounting for these investments using the cost method of accounting. The carrying value of our investments in other entities measured at cost as of December 31, 2017 and 2016 was $19.2 million and $14.6 million , respectively. Patents We capitalize external costs, such as filing fees and associated attorney fees, incurred to obtain issued patents and patent license rights. We expense costs associated with maintaining and defending patents subsequent to their issuance in the period incurred. We amortize capitalized patent costs for internally generated patents on a straight-line basis over ten years, which represents the estimated useful lives of the patents. The ten-year estimated useful life for internally generated patents is based on our assessment of such factors as: the integrated nature of the portfolios being licensed, the overall makeup of the portfolio over time, and the length of license agreements for such patents. The estimated useful lives of acquired patents and patent rights, however, have been and will continue to be based on a separate analysis related to each acquisition and may differ from the estimated useful lives of internally generated patents. The average estimated useful life of acquired patents is 9.8 years. We assess the potential impairment to all capitalized net patent costs when events or changes in circumstances indicate that the carrying amount of our patent portfolio may not be recoverable. At December 31, 2017 and 2016, patents consisted of the following (in thousands, except for useful life data): December 31, 2017 2016 Weighted average estimated useful life (years) 10.0 9.9 Gross patents $ 660,886 $ 593,309 Accumulated amortization (335,478 ) (282,541 ) Patents, net $ 325,408 $ 310,768 Amortization expense related to capitalized patent costs was $52.9 million , $48.6 million and $44.0 million in 2017 , 2016 and 2015 , respectively. These amounts are recorded within the Patent administration and licensing line of our Consolidated Statements of Income. The estimated aggregate amortization expense for the next five years related to our patents balance as of December 31, 2017 is as follows (in thousands): 2018 $ 53,547 2019 50,672 2020 45,871 2021 41,272 2022 38,654 The Company acquired goodwill during 2016 as a result of the acquisition of Hillcrest Labs. Refer to Note 15, " Business Combinations ," for more information regarding this transaction. The carrying value of goodwill at December 31, 2017 and 2016 was $16.0 million and $16.2 million , respectively. These amounts are included in "Other Non-Current Assets" on the Consolidated Balance Sheets. No impairments were recorded during 2017 as a result of our annual goodwill assessment. Other Intangible Assets We capitalize the cost of technology solutions and platforms we acquire or license from third parties when they have a future benefit and the development of these solutions and platforms is substantially complete at the time they are acquired or licensed. Intangible assets consist of acquired patents, existing technology, and trade names. Refer to the above Patents section for more information on acquired patents and existing technology. Our intangible assets are amortized on a straight-line basis over their estimated useful lives, ranging from 9 to 10 years. We make judgments about the recoverability of purchased finite-lived intangible assets whenever facts and circumstances indicate that the useful life is shorter than originally estimated or that the carrying amount of assets may not be recoverable. If such facts and circumstances exist, we assess recoverability by comparing the projected undiscounted net cash flows associated with the related asset or group of assets over their remaining lives against their respective carrying amounts. Impairments, if any, are based on the excess of the carrying amount over the fair value of those assets. If the useful life is shorter than originally estimated, we would accelerate the rate of amortization and amortize the remaining carrying value over the new shorter useful life. Intangible assets excluding patents consisted of the following (in thousands): December 31, 2017 December 31, 2016 Average Life (Years) Gross Assets Accumulated Amortization Net Gross Assets Accumulated Amortization Net Trade Names 9 $ 600 $ (67 ) $ 533 $ 600 $ — $ 600 Customer Relationships 10 1,700 (170 ) 1,530 1,700 — 1,700 $ 2,300 $ (237 ) $ 2,063 (a) $ 2,300 $ — $ 2,300 (a) These amounts are included in "Other Non-Current Assets" on the Consolidated Balance Sheets. Estimated future amortization expense of these intangible assets is as follows (in thousands): 2018 $ 237 2019 237 2020 237 2021 237 2022 237 Thereafter 878 $ 2,063 Revenue Recognition The discussion that follows below is a description of our revenue recognition practices in effect as of December 31, 2017. As discussed in more detail below under “ New Accounting Guidance, " the FASB issued guidance on revenue from contracts with customers that superseded most revenue recognition guidance in effect as of year-end 2017, including industry-specific guidance, which is effective for the Company January 1, 2018. We derive the vast majority of our revenue from patent licensing. The timing and amount of revenue recognized from each licensee depends upon a variety of factors, including the specific terms of each agreement and the nature of the deliverables and obligations. Such agreements are often complex and include multiple elements. These agreements can include, without limitation, elements related to the settlement of past patent infringement liabilities, up-front and non-refundable license fees for the use of patents and/or know-how, patent and/or know-how licensing royalties on covered products sold by licensees, cross-licensing terms between us and other parties, the compensation structure and ownership of intellectual property rights associated with contractual technology development arrangements, advanced payments and fees for service arrangements and settlement of intellectual property enforcement. For agreements entered into or materially modified prior to 2011, due to the inherent difficulty in establishing reliable, verifiable, and objectively determinable evidence of the fair value of the separate elements of these agreements, the total revenue resulting from such agreements has often been recognized over the performance period. Since January 2011, we have accounted for all new or materially modified agreements under the FASB revenue recognition guidance, "Revenue Arrangements with Multiple Deliverables." This guidance requires consideration to be allocated to each element of an agreement that has standalone value using the relative fair value method. In other circumstances, such as those agreements involving consideration for past and expected future patent royalty obligations, after consideration of the particular facts and circumstances, the appropriate recording of revenue between periods may require the use of judgment. In all cases, revenue is only recognized after all of the following criteria are met: (1) written agreements have been executed; (2) delivery of technology or intellectual property rights has occurred or services have been rendered; (3) fees are fixed or determinable; and (4) collectibility of fees is reasonably assured. We establish a receivable for payments expected to be received within twelve months from the balance sheet date based on the terms in the license. Our reporting of such payments often results in an increase to both accounts receivable and deferred revenue. Deferred revenue associated with fixed-fee royalty payments is classified on the balance sheet as short-term when it is scheduled to be amortized within twelve months from the balance sheet date. All other deferred revenue is classified as long-term, as amounts to be recognized over the next twelve months are not known. Patent License Agreements Upon signing a patent license agreement, we provide the licensee permission to use our patented inventions in specific applications. We account for patent license agreements in accordance with the guidance for revenue arrangements with multiple deliverables. We have elected to utilize the leased-based model for revenue recognition, with revenue being recognized over the expected period of benefit to the licensee. Under our patent license agreements, we typically receive one or a combination of the following forms of payment as consideration for permitting our licensees to use our patented inventions in their applications and products: Consideration for Past Patent Royalties: Consideration related to a licensee’s product sales from prior periods may result from a negotiated agreement with a licensee that utilized our patented inventions prior to signing a patent license agreement with us or from the resolution of a disagreement or arbitration with a licensee over the specific terms of an existing license agreement. We may also receive consideration for past patent royalties in connection with the settlement of patent litigation where there was no prior patent license agreement. In each of these cases, we record the consideration as revenue when we have obtained a signed agreement, identified a fixed or determinable price and determined that collectibility is reasonably assured. Fixed-Fee Royalty Payments: These are up-front, non-refundable royalty payments that fulfill the licensee’s obligations to us under a patent license agreement for a specified time period or for the term of the agreement for specified products, under certain patents or patent claims, for sales in certain countries, or a combination thereof — in each case for a specified time period (including for the life of the patents licensed under the agreement). We recognize revenues related to Fixed-Fee Royalty Payments on a straight-line basis over the effective term of the license. We utilize the straight-line method because we cannot reliably predict in which periods, within the term of a license, the licensee will benefit from the use of our patented inventions. Prepayments: These are up-front, non-refundable royalty payments towards a licensee’s future obligations to us related to its expected sales of covered products in future periods. Our licensees’ obligations to pay royalties typically extend beyond the exhaustion of their Prepayment balance. Once a licensee exhausts its Prepayment balance, we may provide them with the opportunity to make another Prepayment toward future sales or it will be required to make Current Royalty Payments. Current Royalty Payments: These are royalty payments covering a licensee’s obligations to us related to its sales of covered products in the current contractual reporting period. Licensees that either owe us Current Royalty Payments or have Prepayment balances are obligated to provide us with quarterly royalty reports that summarize their sales of covered products and their related royalty obligations to us. We typically receive these royalty reports subsequent to the period in which our licensees’ underlying sales occurred. As a result, it is impractical for us to recognize revenue in the period in which the underlying sales occur, and, in most cases, we recognize revenue in the period in which the royalty report is received and other revenue recognition criteria are met due to the fact that without royalty reports from our licensees, our visibility into our licensees’ sales is very limited. When a licensee is required to gross-up their royalty payment to cover applicable foreign withholding tax requirements, the additional consideration is recorded in revenue. The exhaustion of Prepayments and Current Royalty Payments are often calculated based on related per-unit sales of covered products. From time to time, licensees will not report revenues in the proper period, most often due to legal disputes. When this occurs, the timing and comparability of royalty revenue could be affected. In cases where we receive objective, verifiable evidence that a licensee has discontinued sales of products covered under a patent license agreement with us, we recognize any related deferred revenue balance in the period that we receive such evidence. Patent Sales Our business strategy of monetizing our intellectual property includes the sale of select patent assets. As patent sales executed under this strategy represent a component of our ongoing major or central operations and activities, we will record the related proceeds as revenue. We will recognize the revenue when there is persuasive evidence of a sales arrangement, fees are fixed or determinable, delivery has occurred and collectibility is reasonably assured. These requirements are generally fulfilled upon closing of the patent sale transaction. Technology Solutions Technology solutions revenue consists primarily of revenue from royalty payments. We recognize revenue from royalty payments using the same methods described above under our policy for recognizing revenue from patent license agreements. Technology solutions revenues also consist of revenues from software licenses, engineering services and product sales. Software license revenues are recognized in accordance with the original and revised guidance for software revenue recognition. When the arrangement with a customer includes significant production, modification, or customization of the software, we recognize the related revenue using the percentage-of-completion method in accordance with the accounting guidance for construction-type and certain production-type contracts. Under this method, revenue and profit are recognized throughout the term of the contract, based on actual labor costs incurred to date as a percentage of the total estimated labor costs related to the contract. Changes in estimates for revenues, costs and profits are recognized in the period in which they are determinable. When such estimates indicate that costs will exceed future revenues and a loss on the contract exists, a provision for the entire loss is recognized at that time. We recognize revenues associated with engineering service arrangements that are outside the scope of the accounting guidance for construction-type and certain production-type contracts on a straight-line basis, unless evidence suggests that the revenue is earned in a different pattern, over the contractual term of the arrangement or the expected period during which those specified services will be performed, whichever is longer. In such cases we often recognize revenue using proportional performance and measure the progress of our performance based on the relationship between incurred labor hours and total estimated labor hours or other measures of progress, if available. Our most significant cost has been labor and we believe both labor hours and labor cost provide a measure of the progress of our services. The effect of changes to total estimated contract costs is recognized in the period in which such changes are determined. We recognize revenues associated with product sales in the period in which the sales of the underlying units occur. Deferred Charges From time to time, we use sales agents to assist us in our licensing and/or patent sale activities. In such cases, we may pay a commission. The commission rate varies from agreement to agreement. Commissions are normally paid shortly after our receipt of cash payments associated with the patent license or patent sale agreements. We defer recognition of commission expense related to both prepayments and fixed-fee royalty payments and amortize these expenses in proportion to our recognition of the related revenue. In each of 2017 , 2016 and 2015 , we paid cash commissions of less than $0.3 million . Incremental direct costs incurred related to an acquisition or origination of a customer contract

Significant Agreements

Significant Agreements	12 Months Ended
	Dec. 31, 2017
Variable Interest Entity [Line Items]
Legal Matters and Contingencies [Text Block]	SIGNIFICANT AGREEMENTS During fourth quarter 2017, we entered into a multi-year, worldwide, non-exclusive patent license with LG (the “LG PLA”), a global leader and technology innovator in consumer electronics, mobile communications and home appliances. The LG PLA covers the 3G, 4G and 5G terminal unit products of LG and its affiliates and sets forth a royalty of cash payments to InterDigital as well as a process for the transfer of patents from LG to InterDigital. The deal also commits the parties to explore cooperation for projects related to the research and development of video and sensor technology for connected and autonomous vehicles. In addition, the parties also agreed to terms for dismissal by InterDigital of the outstanding litigation among the parties and their affiliates. Our agreement with LG is a multiple-element arrangement for accounting purposes. We recognized $42.4 million of revenue under this patent license agreement during 2017, including $34.5 million of past sales. We will recognize future revenue under the agreement on a straight-line basis over its term. A portion of the consideration for the agreement was in the form of patents from LG. Refer to Note 2, " Summary of Significant Accounting Policies ," for additional information related to the estimates and methods used to determine the fair value of the patents acquired. Consistent with the revenue recognition policy disclosed in Note 2, " Summary of Significant Accounting Policies ," we identified each element of the LG PLA, estimated its relative value for purposes of allocating the arrangement consideration and determined when each of those elements should be recognized. Using the accounting guidance applicable to multiple-element revenue arrangements, we allocated the consideration to each element for accounting purposes using our best estimate of the term and value of each element. The development of a number of these inputs and assumptions in the models requires a significant amount of management judgment and is based upon a number of factors, including the assumed royalty rates, sales volumes, discount rate and other relevant factors. Changes in any of a number of these assumptions could have had a substantial impact on the relative fair value assigned to each element for accounting purposes. These inputs and assumptions represent management's best estimates at the time of the transaction.

Geographic Concentration

Geographic Concentration	12 Months Ended
	Dec. 31, 2017
GEOGRAPHIC CUSTOMER CONCENTRATION [Abstract]
Segment Reporting Disclosure [Text Block]	GEOGRAPHIC / CUSTOMER CONCENTRATION We have one reportable segment.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2017
Property and Equipment [Abstract]
Property, Plant and Equipment Disclosure [Text Block]	5. PROPERTY AND EQUIPMENT Property and equipment, net is comprised of the following (in thousands): December 31, 2017 2016 Computer equipment and software $ 20,003 $ 18,480 Engineering and test equipment 4,034 3,767 Building and improvements 3,624 3,576 Leasehold improvements 9,711 9,692 Furniture and fixtures 1,279 1,247 Property and equipment, gross 38,651 36,762 Less: accumulated depreciation (27,978 ) (24,136 ) Property and equipment, net $ 10,673 $ 12,626 Depreciation expense was $3.9 million , $4.1 million and $3.8 million in 2017 , 2016 and 2015 , respectively. Depreciation expense included depreciation of computer software costs of $0.5 million , $1.0 million and $1.4 million in 2017 , 2016 and 2015 , respectively. Accumulated depreciation related to computer software costs was $8.8 million and $8.4 million at December 31, 2017 and 2016 , respectively. The net book value of our computer software was $0.5 million and $1.0 million at December 31, 2017 and 2016 , respectively.

Obligations

Obligations	12 Months Ended
	Dec. 31, 2017
OBLIGATIONS: [Abstract]
Long-term Debt [Text Block]	6. OBLIGATIONS Long-term debt obligations are comprised of the following (in thousands): December 31, 2017 2016 1.50% Senior Convertible Notes due 2020 $ 316,000 $ 316,000 Less: Unamortized interest discount (27,863 ) (39,578 ) Deferred financing costs (3,011 ) (4,401 ) Total debt obligations 285,126 272,021 Less: Current portion of long-term debt — — Long-term debt obligations $ 285,126 $ 272,021 There were no capital leases at December 31, 2017 or December 31, 2016 . Maturities of principal of the long-term debt obligations of the Company as of December 31, 2017 are as follows (in thousands): 2018 $ — 2019 — 2020 316,000 2021 — 2022 — Thereafter — $ 316,000 2016 Senior Convertible Notes, and Related Note Hedge and Warrant Transactions In April 2011, we issued $230.0 million in aggregate principal amount of 2.50% Senior Convertible Notes due 2016 (the “2016 Notes”), which matured and were repaid in full on March 15, 2016. In connection with the offering of the 2016 Notes, on March 29 and March 30, 2011, we entered into convertible note hedge transactions that covered, subject to customary anti-dilution adjustments, approximately 3.5 million and approximately 0.5 million shares of our common stock, respectively, at an initial strike price that corresponded to the initial conversion price of the 2016 Notes and were exercisable upon conversion of the 2016 Notes. In addition, on the same dates, we sold warrants to acquire, subject to customary anti-dilution adjustments, approximately 3.5 million shares and approximately 0.5 million shares, respectively, of common stock. The warrants had a final strike price of $62.95 per share, as adjusted in August 2016. The warrants became exercisable and expired in daily tranches from June 15, 2016 through August 10, 2016. The market price of our common stock did not exceed the strike price of the warrants on any warrant expiration date in second quarter 2016; during third quarter 2016, we issued 23,667 shares of common stock pursuant to these warrants. Accounting Treatment of the 2016 Notes and Related Convertible Note Hedge and Warrant Transactions The offering of the 2016 Notes on March 29, 2011 was for $200.0 million and included an overallotment option that allowed the initial purchaser to purchase up to an additional $30.0 million aggregate principal amount of 2016 Notes. The initial purchaser exercised its overallotment option on March 30, 2011, bringing the total amount of 2016 Notes issued on April 4, 2011 to $230.0 million . In connection with the offering of the 2016 Notes, as discussed above, the Company entered into convertible note hedge transactions with respect to its common stock. The $42.7 million cost of the convertible note hedge transactions was partially offset by the proceeds from the sale of the warrants described above, resulting in a net cost of $10.9 million . Existing accounting guidance provides that the March 29, 2011 convertible note hedge and warrant contracts be treated as derivative instruments for the period during which the initial purchaser's overallotment option was outstanding. Once the overallotment option was exercised on March 30, 2011, the March 29, 2011 convertible note hedge and warrant contracts were reclassified to equity, as the settlement terms of the Company's note hedge and warrant contracts both provide for net share settlement. There was no material net change in the value of these convertible note hedges and warrants during the one day they were classified as derivatives and the equity components of these instruments will not be adjusted for subsequent changes in fair value. Under current accounting guidance, the Company bifurcated the proceeds from the offering of the 2016 Notes between the liability and equity components of the debt. On the date of issuance, the liability and equity components were calculated to be approximately $187.0 million and $43.0 million , respectively. The initial $187.0 million liability component was determined based on the fair value of similar debt instruments excluding the conversion feature. The initial $43.0 million ( $28.0 million net of tax) equity component represents the difference between the fair value of the initial $187.0 million in debt and the $230.0 million of gross proceeds. The related initial debt discount of $43.0 million was being amortized using the effective interest method over the life of the 2016 Notes. An effective interest rate of 7% was used to calculate the debt discount on the 2016 Notes. In connection with the above-noted transactions, the Company incurred $8.0 million of directly related costs. The initial purchaser's transaction fees and related offering expenses were allocated to the liability and equity components of the debt in proportion to the allocation of proceeds and accounted for as debt issuance costs. We allocated $6.5 million of debt issuance costs to the liability component of the debt, which were capitalized as deferred financing costs. These costs were amortized to interest expense over the term of the debt using the effective interest method. The remaining $1.5 million of costs allocated to the equity component of the debt were recorded as a reduction of the equity component of the debt. 2020 Senior Convertible Notes, and Related Note Hedge and Warrant Transactions On March 11, 2015, we issued $316.0 million in aggregate principal amount of 1.50% Senior Convertible Notes due 2020 (the “2020 Notes”). The 2020 Notes bear interest at a rate of 1.50% per year, payable in cash on March 1 and September 1 of each year, commencing September 1, 2015, and mature on March 1, 2020, unless earlier converted or repurchased. The 2020 Notes will be convertible into cash, shares of our common stock or a combination thereof, at our election, at a current conversion rate of 13.8664 shares of common stock per $1,000 principal amount of 2020 Notes (which is equivalent to a conversion price of approximately $72.12 per share). as adjusted pursuant to the terms of the indenture for the 2020 Notes (the "Indenture"). The conversion rate, and thus the conversion price, may be adjusted under certain circumstances, including in connection with conversions made following certain fundamental changes and under other circumstances set forth in the Indenture. It is our current intent and policy to settle all conversions through combination settlement of cash and shares of common stock, with a specified dollar amount of $1,000 per $1,000 principal amount of the 2020 Notes and any remaining amounts in shares. Prior to 5:00 p.m., New York City time, on the business day immediately preceding December 1, 2019, the 2020 Notes will be convertible only under certain circumstances as set forth in the indenture to the 2020 Notes, including on any date during any calendar quarter (and only during such calendar quarter) if the closing sale price of our common stock was more than 130% of the applicable conversion price (approximately $93.76 based on the current conversion price) on each applicable trading day for at least 20 trading days in the period of the 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter. Commencing on December 1, 2019, the 2020 Notes will be convertible in multiples of $1,000 principal amount, at any time prior to 5:00 p.m., New York City time, on the second scheduled trading day immediately preceding the maturity date of the 2020 Notes. The Company may not redeem the 2020 Notes prior to their maturity date. On March 5 and March 9, 2015, in connection with the offering of the 2020 Notes, we entered into convertible note hedge transactions that cover approximately 3.8 million and approximately 0.6 million shares of our common stock, respectively, and they have a strike price that corresponds to the conversion price of the 2020 Notes and are exercisable upon conversion of the 2020 Notes. The cost of the March 5 and March 9, 2015 convertible note hedge transactions was approximately $51.7 million and approximately $7.7 million , respectively. On March 5 and March 9, 2015, we sold warrants to acquire approximately 3.8 million and approximately 0.6 million , respectively, of common stock, subject to customary anti-dilution adjustments. As of December 31, 2017, the warrants had a strike price of approximately $88.03 per share, as adjusted. The warrants become exercisable and expire in daily tranches over a three-and-a-half-month period starting in June 2020. As consideration for the warrants issued on March 5 and March 9, 2015, we received approximately $37.3 million and approximately $5.6 million , respectively. The Company also repurchased 0.8 million shares of our common stock at $53.61 per share, the closing price of the stock on March 5, 2015, from institutional investors through one of the initial purchasers and its affiliate, as our agent, concurrently with the pricing of the offering of the 2020 Notes. Accounting Treatment of the 2020 Notes and Related Convertible Note Hedge and Warrant Transactions The offering of the 2020 Notes on March 5, 2015 was for $275.0 million and included an overallotment option that allowed the initial purchasers to purchase up to an additional $41.0 million aggregate principal amount of 2020 Notes. The initial purchasers exercised their overallotment option on March 9, 2015, bringing the total amount of 2020 Notes issued on March 11, 2015 to $316.0 million . In connection with the offering of the 2020 Notes, as discussed above, InterDigital entered into convertible note hedge transactions with respect to its common stock. The $59.4 million cost of the convertible note hedge transactions was partially offset by the proceeds from the sale of the warrants described above, resulting in a net cost of $16.5 million . Both the convertible note hedge and warrants were classified as equity. The Company bifurcated the proceeds from the offering of the 2020 Notes between liability and equity components. On the date of issuance, the liability and equity components were calculated to be approximately $256.7 million and $59.3 million , respectively. The initial $256.7 million liability component was determined based on the fair value of similar debt instruments excluding the conversion feature. The initial $59.3 million ( $38.6 million net of tax) equity component represents the difference between the fair value of the initial $256.7 million in debt and the $316.0 million of gross proceeds. The related initial debt discount of $59.3 million is being amortized using the effective interest method over the life of the 2020 Notes. An effective interest rate of 5.89% was used to calculate the debt discount on the 2020 Notes. In connection with the above-noted transactions, the Company incurred $9.3 million of directly related costs. The initial purchasers' transaction fees and related offering expenses were allocated to the liability and equity components in proportion to the allocation of proceeds and accounted for as debt and equity issuance costs, respectively. We allocated $7.0 million of debt issuance costs to the liability component, which were capitalized as deferred financing costs. These costs are being amortized to interest expense over the term of the debt using the effective interest method. The remaining $2.4 million of costs allocated to the equity component were recorded as a reduction of the equity component. The following table presents the amount of interest cost recognized for the years ended December 31, 2017 , 2016 and 2015 related to the contractual interest coupon, accretion of the debt discount and the amortization of financing costs (in thousands). For the Year Ended December 31, 2017 2016 2015 Contractual coupon interest $ 4,740 $ 6,178 $ 9,568 Accretion of debt discount 11,715 13,536 18,384 Amortization of financing costs 1,390 1,716 2,485 Total $ 17,845 $ 21,430 $ 30,437

Commitments

Commitments	12 Months Ended
	Dec. 31, 2017
COMMITMENTS [Abstract]
Commitments Disclosure [Text Block]	COMMITMENTS We have entered into various operating lease agreements. Total rent expense, primarily for office space, was $3.9 million , $4.2 million and $3.3 million in 2017 , 2016 and 2015 , respectively. Minimum future payments for operating leases and purchase commitments as of December 31, 2017 are as follows (in thousands): 2018 $ 4,784 2019 4,499 2020 2,918 2021 2,377 2022 2,131 Thereafter 4,741

Litigation and Legal Proceeding

Litigation and Legal Proceedings (Notes)	12 Months Ended
	Dec. 31, 2017
4. LITIGATION AND LEGAL PROCEEDINGS [Abstract]
Legal Matters and Contingencies [Text Block]	8. LITIGATION AND LEGAL PROCEEDINGS ARBITRATIONS AND COURT PROCEEDINGS (OTHER THAN DE DISTRICT COURT ACTIONS RELATED TO USITC PROCEEDINGS) Huawei China Proceedings On February 21, 2012, InterDigital was served with two complaints filed by Huawei Technologies Co., Ltd. in the Shenzhen Intermediate People's Court in China on December 5, 2011. The first complaint named as defendants InterDigital, Inc. and its wholly owned subsidiaries InterDigital Technology Corporation and InterDigital Communications, LLC (now InterDigital Communications, Inc.), and alleged that InterDigital had abused its dominant market position in the market for the licensing of essential patents owned by InterDigital by engaging in allegedly unlawful practices, including differentiated pricing, tying and refusal to deal. The second complaint named as defendants the Company's wholly owned subsidiaries InterDigital Technology Corporation, InterDigital Communications, LLC (now InterDigital Communications, Inc.), InterDigital Patent Holdings, Inc. and IPR Licensing, Inc. and alleged that InterDigital had failed to negotiate on FRAND terms with Huawei. Huawei asked the court to determine the FRAND rate for licensing essential Chinese patents to Huawei and also sought compensation for its costs associated with this matter. On February 4, 2013, the Shenzhen Intermediate People's Court issued rulings in the two proceedings. With respect to the first complaint, the court decided that InterDigital had violated the Chinese Anti-Monopoly Law by (i) making proposals for royalties from Huawei that the court believed were excessive, (ii) tying the licensing of essential patents to the licensing of non-essential patents, (iii) requesting as part of its licensing proposals that Huawei provide a grant-back of certain patent rights to InterDigital and (iv) commencing a USITC action against Huawei while still in discussions with Huawei for a license. Based on these findings, the court ordered InterDigital to cease the alleged excessive pricing and alleged improper bundling of InterDigital's Chinese essential and non-essential patents, and to pay Huawei 20.0 million RMB (approximately $3.2 million) in damages related to attorneys’ fees and other charges, without disclosing a factual basis for its determination of damages. The court dismissed Huawei's remaining allegations, including Huawei's claim that InterDigital improperly sought a worldwide license and improperly sought to bundle the licensing of essential patents on multiple generations of technologies. With respect to the second complaint, the court determined that, despite the fact that the FRAND requirement originates from ETSI's Intellectual Property Rights policy, which refers to French law, InterDigital's license offers to Huawei should be evaluated under Chinese law. Under Chinese law, the court concluded that the offers did not comply with FRAND. The court further ruled that the royalties to be paid by Huawei for InterDigital's 2G, 3G and 4G essential Chinese patents under Chinese law should not exceed 0.019% of the actual sales price of each Huawei product. On March 11, 2013, InterDigital filed notices of appeal with respect to the judgments in both proceedings, seeking reversal of the court’s February 4, 2013 rulings. On October 16, 2013, the Guangdong Province High Court issued a ruling affirming the ruling of the Shenzhen Intermediate People's Court in the second proceeding, and on October 21, 2013, issued a ruling affirming the ruling of the Shenzhen Intermediate People's Court in the first proceeding. InterDigital believes that the decisions are seriously flawed both legally and factually. For instance, in determining a purported FRAND rate, the Chinese courts applied an incorrect economic analysis by evaluating InterDigital’s lump-sum 2007 patent license agreement with Apple (the “2007 Apple PLA”) in hindsight to posit a running royalty rate. Indeed, the ALJ in USITC Inv. No. 337-TA-800 rejected that type of improper analysis. Moreover, the Chinese courts had an incomplete record and applied incorrect facts, including with respect to the now-expired and superseded 2007 Apple PLA, which had been found in an arbitration between InterDigital and Apple to be limited in scope. On April 14, 2014, InterDigital filed a petition for retrial of the second proceeding with the Chinese Supreme People’s Court (“SPC”), seeking dismissal of the judgment or at least a higher, market-based royalty rate for a license to InterDigital’s Chinese standards-essential patents (“SEPs”). The petition for retrial argues, for example, that (1) the lower court improperly determined a Chinese FRAND running royalty rate by using as a benchmark the 2007 Apple lump sum fixed payment license agreement, and looking in hindsight at the unexpectedly successful sales of Apple iPhones to construct an artificial running royalty rate that neither InterDigital nor Apple could have intended and that would have varied significantly depending on the relative success or failure in hindsight of Apple iPhone sales; (2) the 2007 Apple PLA was also an inappropriate benchmark because its scope of product coverage was significantly limited as compared to the license that the court was considering for Huawei, particularly when there are other more comparable license agreements; and (3) if the appropriate benchmarks had been used, and the court had considered the range of royalties offered by other similarly situated SEP holders in the wireless telecommunications industry, the court would have determined a FRAND royalty that was substantially higher than 0.019%, and would have found, consistent with findings of the ALJ’s initial determination in the USITC 337-TA-800 proceeding, that there was no proof that InterDigital’s offers to Huawei violated its FRAND commitments. The SPC held a hearing on October 31, 2014, regarding whether to grant a retrial and requested that both parties provide additional information regarding the facts and legal theories underlying the case. The SPC convened a second hearing on April 1, 2015 regarding whether to grant a retrial. If the retrial is granted, the SPC will likely schedule one or more additional hearings before it issues a decision on the merits of the case. The SPC retrial proceeding was excluded from the dismissal provisions of the August 2016 patent license agreement between Huawei and InterDigital, and a decision in this proceeding is still pending. ZTE China Proceedings On July 10 and 11, 2014, InterDigital was served with two complaints filed by ZTE Corporation in the Shenzhen Intermediate People's Court in China on April 3, 2014. The first complaint names as defendants the Company's wholly owned subsidiaries InterDigital Technology Corporation, InterDigital Communications, Inc., InterDigital Patent Holdings, Inc. and IPR Licensing, Inc. This complaint alleges that InterDigital has failed to comply with its FRAND obligations for the licensing of its Chinese standards-essential patents. ZTE is asking the court to determine the FRAND rate for licensing InterDigital’s standards-essential Chinese patents to ZTE and also seeks compensation for its litigation costs associated with this matter. The second complaint names as defendants InterDigital, Inc. and its wholly owned subsidiaries InterDigital Technology Corporation and InterDigital Communications, Inc. This complaint alleges that InterDigital has a dominant market position in China and the United States in the market for the licensing of essential patents owned by InterDigital, and abused its dominant market position in violation of the Chinese Anti-Monopoly Law by engaging in allegedly unlawful practices, including excessively high pricing, tying, discriminatory treatment, and imposing unreasonable trading conditions. ZTE seeks relief in the amount of 20.0 million RMB (approximately $3.1 million based on the exchange rate as of December 31, 2017), an order requiring InterDigital to cease the allegedly unlawful conduct and compensation for its litigation costs associated with this matter. On August 7, 2014, InterDigital filed petitions challenging the jurisdiction of the Shenzhen Intermediate People's Court to hear the actions. On August 28, 2014, the court denied InterDigital’s jurisdictional challenge with respect to the anti-monopoly law case. InterDigital filed an appeal of this decision on September 26, 2014. On September 28, 2014, the court denied InterDigital’s jurisdictional challenge with respect to the FRAND case, and InterDigital filed an appeal of that decision on October 27, 2014. On December 18, 2014, the Guangdong High Court issued decisions on both appeals upholding the Shenzhen Intermediate Court’s decisions that it had jurisdiction to hear these cases. On February 10, 2015, InterDigital filed a petition for retrial with the Supreme People’s Court regarding its jurisdictional challenges to both cases. The Shenzhen Court held hearings on the anti-monopoly law case on May 11, 13, 15 and 18, 2015. At the May hearings, ZTE withdrew its claims alleging discriminatory treatment and the imposition of unfair trading conditions and increased its damages claim to 99.8 million RMB (approximately $15.3 million based on the exchange rate as of December 31, 2017). The Shenzhen Court held hearings in the FRAND case on July 29-31, 2015 and held a second hearing on the anti-monopoly law case on October 12, 2015. Both cases remain pending. It is possible that the court may schedule further hearings in these cases before issuing its decisions. The Company has not recorded any accrual at December 31, 2017 for contingent losses associated with these matters based on its belief that losses, while reasonably possible, are not probable in accordance with accounting guidance. Pegatron Actions In first quarter 2015, we learned that on or about February 3, 2015, Pegatron Corporation (“Pegatron”) filed a civil suit in Taiwan Intellectual Property Court against InterDigital, Inc. and certain of its subsidiaries alleging breach of the Taiwan Fair Trade Act (the “Pegatron Taiwan Action”). Pegatron and InterDigital entered into a patent license agreement in April 2008 (the “Pegatron PLA”). Pegatron was a subsidiary of Asustek Computer Incorporated until the completion of its spin-off from Asustek in June 2010. On May 26, 2015, InterDigital, Inc. received a copy of the civil complaint filed by Pegatron in the Taiwan Intellectual Property Court. The complaint named as defendants InterDigital, Inc. as well as InterDigital’s wholly owned subsidiaries InterDigital Technology Corporation and IPR Licensing, Inc. (together, for purposes of this discussion, “InterDigital”). The complaint alleged that InterDigital abused its market power by improperly setting, maintaining or changing the royalties Pegatron is required to pay under the Pegatron PLA, and engaging in unreasonable discriminatory treatment and other unfair competition activities in violation of the Taiwan Fair Trade Act. The complaint sought minimum damages in the amount of approximately $52 million, which amount could be expanded during the litigation, and that the court order multiple damages based on its claim that the alleged conduct was intentional. The complaint also sought an order requiring InterDigital to cease enforcing the royalty provisions of the Pegatron PLA, as well as all other conduct that allegedly violates the Fair Trade Act. On June 5, 2015, InterDigital filed an Arbitration Demand with the American Arbitration Association’s International Centre for Dispute Resolution (“ICDR”) seeking declaratory relief denying all of the claims in Pegatron’s Taiwan Action and for breach of contract. On or about June 10, 2015, InterDigital filed a complaint in the United States District Court for the Northern District of California, San Jose Division (the “CA Northern District Court”) seeking a Temporary Restraining Order, Preliminary Injunction, and Permanent Anti-suit Injunction against Pegatron prohibiting Pegatron from prosecuting the Pegatron Taiwan Action. The complaint also sought specific performance by Pegatron of the dispute resolution procedures set forth in the Pegatron PLA and compelling arbitration of the disputes in the Pegatron Taiwan Action. On June 29, 2015, the court granted InterDigital’s motion for a temporary restraining order and preliminary injunction requiring Pegatron take immediate steps to dismiss the Taiwan Action without prejudice. On July 1, 2015, InterDigital was informed that Pegatron had withdrawn its complaint in the Taiwan Intellectual Property Court and that the case had been dismissed without prejudice. On August 3, 2015, Pegatron filed an answer and counterclaims to InterDigital’s CA Northern District Court complaint. Pegatron accused InterDigital of violating multiple sections of the Taiwan Fair Trade Act, violating Section Two of the Sherman Act, breaching ETSI, IEEE, and ITU contracts, promissory estoppel (pled in the alternative), violating Section 17200 of the California Business & Professions Code, and violating the Delaware Consumer Fraud Act. These counterclaims stemmed from Pegatron’s accusation that InterDigital violated FRAND obligations. As relief, Pegatron sought a declaration regarding the appropriate FRAND terms and conditions for InterDigital’s “declared essential patents,” a declaration that InterDigital’s standard essential patents are unenforceable due to patent misuse, an order requiring InterDigital to grant Pegatron a license on FRAND terms, an order enjoining InterDigital’s alleged ongoing breaches of its FRAND commitments, and damages in the amount of allegedly excess non-FRAND royalties Pegatron has paid to InterDigital, plus interest and treble damages. On August 7, 2015, Pegatron responded to InterDigital’s arbitration demand, disputing the arbitrability of Pegatron’s claims. On September 24, 2015, InterDigital moved to compel arbitration and dismiss Pegatron’s counterclaims or, in the alternative, stay the counterclaims pending the parties’ arbitration. Pegatron’s opposition to this motion was filed on October 22, 2015, and InterDigital’s reply was filed on November 12, 2015. On January 20, 2016, the court granted InterDigital’s motion to compel arbitration of Pegatron’s counterclaims and to stay the counterclaims pending the arbitrators’ determination of their arbitrability. On January 27, 2016, the parties stipulated to stay all remaining aspects of the CA Northern District case pending such an arbitrability determination. On the same day, the court granted the stay and administratively closed the case. On October 14, 2016, Pegatron filed in the arbitration a motion to dismiss for lack of jurisdiction, arguing that Pegatron’s counterclaims and InterDigital’s corresponding declaratory judgment claims were not arbitrable. Following briefing and an oral argument, on September 18, 2017, the tribunal issued a Partial Final Award and determined by majority decision that none of Pegatron’s counterclaims, nor InterDigital’s related claim for declaratory relief, are arbitrable. In light of the arbitral award regarding jurisdiction, Pegatron’s claims returned to the CA Northern District Court. InterDigital answered and denied all of Pegatron’s counterclaims and filed a counterclaim-in-reply on December 1, 2017. On December 22, 2017, Pegatron answered and denied InterDigital’s counterclaim-in-reply. On January 16, 2018, InterDigital entered into an amended patent license agreement and settlement agreement with Pegatron, pursuant to which the parties agreed to terms for dismissal of all outstanding litigation and other proceedings among them. On January 22, 2018, the parties filed a stipulation of dismissal of the CA Northern District case. On the same day, the court granted the stipulation and dismissed the case with prejudice. The parties also terminated the arbitration on January 22, 2018. Asustek Actions On April 15, 2015, Asustek Computer Incorporated (“Asus”) filed a complaint in the CA Northern District Court against InterDigital, Inc., and its subsidiaries InterDigital Communications, Inc., InterDigital Technology Corporation, IPR Licensing, Inc., and InterDigital Patent Holdings, Inc. The complaint asserted the following causes of action: violation of Section Two of the Sherman Act, violation of Section 17200 of the California Business and Professions Code, breach of contract resulting from ongoing negotiations, breach of contract leading to and resulting in the parties’ April 2008 patent license agreement (the “2008 Asus PLA”), promissory estoppel, waiver, and fraudulent inducement to contract. Among other allegations, Asus alleged that InterDigital breached its FRAND commitment. As relief, Asus sought a judgment that the 2008 Asus PLA is void or unenforceable, damages in the amount of excess royalties Asus paid under the 2008 Asus PLA plus interest, a judgment setting the proper FRAND terms and conditions for InterDigital’s patent portfolio, an order requiring InterDigital to grant Asus a license on FRAND terms and conditions, and punitive damages and other relief. In response, on May 30, 2015, InterDigital filed an Arbitration Demand with the ICDR. InterDigital claimed that Asus breached the 2008 Asus PLA’s dispute resolution provision by filing its CA Northern District Court lawsuit and sought declaratory relief that it is not liable for any of the claims in Asus’s complaint. On June 2, 2015, InterDigital filed in the CA Northern District Court a motion to compel arbitration on each of Asus’s claims. On August 25, 2015, the court granted InterDigital’s motion for all of Asus’s claims except its claim for breach of contract resulting from ongoing negotiations. Aside from this claim, the court ruled that the issue of arbitrability should be decided by an arbitrator, and stayed the proceedings pending that determination. Asus asserted counterclaims in the arbitration that mirrored its CA Northern District Court claims, except that it did not assert the breach of contract claim that the court determined was not arbitrable and it added a claim of violation of the Delaware Consumer Fraud Act. Asus also contended that its counterclaims were not arbitrable. InterDigital added a claim for breach of the 2008 Asus PLA’s confidentiality provision. On July 14, 2016, Asus filed a motion to lift the stay in the CA Northern District Court proceeding along with a notice of the arbitral tribunal’s decision on arbitrability, informing the court of the arbitrators’ decision that, other than InterDigital’s breach of contract claims and Asus’s fraudulent inducement claim, no other claim or counterclaim is arbitrable. Asus then filed in the CA Northern District Court an amended complaint on August 18, 2016. This amended complaint includes all of the claims in Asus’s first CA Northern District Court complaint except fraudulent inducement and adds a claim of violation of the Delaware Consumer Fraud Act. It seeks the same relief as its first CA Northern District Court complaint, but also seeks a ruling that each of InterDigital’s patents “declared [to standards-setting organizations] to be essential or potentially essential” is unenforceable and any contracts InterDigital entered into in furtherance of its unlawful conduct are void. On September 8, 2016, InterDigital filed its answer and counterclaims to Asus’s amended complaint. It denied Asus’s claims and filed a counterclaim for declaratory judgment that Asus’s tort claims are invalid or preempted as applied under the First Amendment to the U.S. Constitution, the Patent Clause of the U.S. Constitution, and Title 35 of the U.S. Code. On September 28, 2016, Asus answered and denied InterDigital’s counterclaims. On December 16, 2016, the court set a case schedule that includes a May 2019 trial date. With respect to its arbitration counterclaim for fraudulent inducement, Asus stated in its pleadings that it was seeking return of excess royalties (which totaled close to $63 million as of the August 2016 date referenced in the pleadings and had increased with additional royalty payments made by Asus since such time), plus interest, costs and attorneys’ fees. The evidentiary hearing in the arbitration was held in January 2017, and the parties presented oral closing arguments on March 22, 2017. On August 2, 2017, the arbitral tribunal issued its Final Award. The tribunal fully rejected Asus’s counterclaim, finding that InterDigital did not fraudulently induce Asus to enter into the 2008 Asus PLA. Accordingly, the tribunal dismissed Asus’s fraudulent inducement counterclaim in its entirety. The tribunal also dismissed InterDigital’s claims that Asus breached the confidentiality provisions and the dispute resolution provisions of the 2008 Asus PLA. On October 20, 2017, InterDigital and Asus jointly moved to confirm both the tribunal’s Final Award and the Interim Award on Jurisdiction in the CA Northern District. The court confirmed both awards on October 25, 2017. REGULATORY PROCEEDINGS Investigation by National Development and Reform Commission of China On September 23, 2013, counsel for InterDigital was informed by China’s National Development and Reform Commission (“NDRC”) that the NDRC had initiated a formal investigation into whether InterDigital has violated China’s Anti-Monopoly Law (“AML”) with respect to practices related to the licensing of InterDigital’s standards-essential patents to Chinese companies. Companies found to violate the AML may be subject to a cease and desist order, fines and disgorgement of any illegal gains. On March 3, 2014, the Company submitted to NDRC, pursuant to a procedure set out in the AML, a formal application for suspension of the investigation that included proposed commitments by the Company. On May 22, 2014, NDRC formally suspended its investigation of the Company based on the commitments proposed by the Company. The Company’s commitments with respect to the licensing of its patent portfolio for wireless mobile standards to Chinese manufacturers of cellular terminal units (“Chinese Manufacturers”) are as follows: 1. Whenever InterDigital engages with a Chinese Manufacturer to license InterDigital’s patent portfolio for 2G, 3G and 4G wireless mobile standards, InterDigital will offer such Chinese Manufacturer the option of taking a worldwide portfolio license of only its standards-essential wireless patents, and comply with F/RAND principles when negotiating and entering into such licensing agreements with Chinese Manufacturers. 2. As part of its licensing offer, InterDigital will not require that a Chinese Manufacturer agree to a royalty-free, reciprocal cross-license of such Chinese Manufacturer's similarly categorized standards-essential wireless patents. 3. Prior to commencing any action against a Chinese Manufacturer in which InterDigital may seek exclusionary or injunctive relief for the infringement of any of its wireless standards-essential patents, InterDigital will offer such Chinese Manufacturer the option to enter into expedited binding arbitration under fair and reasonable procedures to resolve the royalty rate and other terms of a worldwide license under InterDigital's wireless standards-essential patents. If the Chinese Manufacturer accepts InterDigital's binding arbitration offer or otherwise enters into an agreement with InterDigital on a binding arbitration mechanism, InterDigital will, in accordance with the terms of the arbitration agreement and patent license agreement, refrain from seeking exclusionary or injunctive relief against such company. The commitments contained in item 3 above will expire five years from the effective date of the suspension of the investigation, or May 22, 2019. USITC PROCEEDINGS AND RELATED DELAWARE DISTRICT COURT PROCEEDINGS 2013 USITC Proceeding (337-TA-868) and Related ZTE Delaware District Court Proceeding USITC Proceeding (337-TA-868) On January 2, 2013, the Company’s wholly owned subsidiaries InterDigital Communications, Inc., InterDigital Technology Corporation, IPR Licensing, Inc. and InterDigital Holdings, Inc. filed a complaint with the United States International Trade Commission (the “USITC” or “Commission”) against Samsung Electronics Co., Ltd., Samsung Electronics America, Inc. and Samsung Telecommunications America, LLC, Nokia Corporation and Nokia Inc., Huawei Technologies Co., Ltd., Huawei Device USA, Inc. and FutureWei Technologies, Inc. d/b/a Huawei Technologies (USA) and ZTE Corporation and ZTE (USA) Inc. (collectively, the “337-TA-868 Respondents”), alleging violations of Section 337 of the Tariff Act of 1930 in that they engaged in unfair trade practices by selling for importation into the United States, importing into the United States and/or selling after importation into the United States certain 3G and 4G wireless devices (including WCDMA-, cdma2000- and LTE-capable mobile phones, USB sticks, mobile hotspots, laptop computers and tablets and components of such devices) that infringe one or more of up to seven of InterDigital’s U.S. patents. The complaint also extended to certain WCDMA and cdma2000 devices incorporating Wi-Fi functionality. InterDigital’s complaint with the USITC sought an exclusion order that would bar from entry into the United States infringing 3G or 4G wireless devices (and components), including LTE devices, that are imported by or on behalf of the 337-TA-868 Respondents, and also sought a cease-and-desist order to bar further sales of infringing products that have already been imported into the United States. Certain of the asserted patents were also asserted against Nokia, Huawei and ZTE in earlier pending USITC proceedings (including the Nokia, Huawei and ZTE 2011 USITC Proceeding (337-TA-800) and the Nokia 2007 USITC Proceeding (337-TA-613), as set forth below) and therefore were not asserted against those 337-TA-868 Respondents in this investigation. On December 23, 2013, InterDigital and Huawei reached a settlement agreement to enter into binding arbitration to resolve their global patent licensing disputes. Pursuant to the settlement agreement, InterDigital and Huawei moved to dismiss all litigation matters pending between the parties except the action filed by Huawei in China to set a fair, reasonable and non-discriminatory (“FRAND”) rate for the licensing of InterDigital’s Chinese standards-essential patents (discussed above under “Huawei China Proceedings”), the decision in which InterDigital is permitted to further appeal. As a result, effective February 12, 2014, the Huawei Respondents were terminated from the 337-TA-868 investigation. From February 10 to February 20, 2014, ALJ Essex presided over the evidentiary hearing in this investigation. The patents in issue in this investigation as of the hearing were U.S. Patent Nos. 7,190,966 (the “’966 patent”) and 7,286,847 (the “’847 patent”) asserted against ZTE and Samsung, and U.S. Patent No. 7,941,151 (the “’151 patent”) asserted against ZTE, Samsung and Nokia. On June 3, 2014, InterDigital and Samsung filed a joint motion to terminate the investigation as to Samsung on the basis of settlement. The ALJ granted the joint motion by initial determination issued on June 9, 2014, and the USITC determined not to review the initial determination on June 30, 2014. On June 13, 2014, the ALJ issued an Initial Determination (“ID”) in the 337-TA-868 investigation. In the ID, the ALJ found that no violation of Section 337 had occurred in connection with the importation of 3G/4G devices by ZTE or Nokia, on the basis that the accused devices do not infringe asserted claims 1-6, 8-9, 16-21 or 23-24 of the ’151 patent, claims 1, 3, 6, 8, 9, or 11 of the ’966 patent, or claims 3 or 5 of the ’847 patent. The ALJ also found that claim 16 of the ’151 patent was invalid as indefinite. Among other determinations, the ALJ further determined that InterDigital did not violate any FRAND obligations, a conclusion also reached by the ALJ in the 337-TA-800 investigation, and that Respondents have engaged in patent “hold out.” On June 30, 2014, InterDigital filed a Petition for Review with the USITC seeking review and reversal of certain of the ALJ’s conclusions in the ID. On the same day, Respondents filed a Conditional Petition for Review urging alternative grounds for affirmance of the ID’s finding that Section 337 was not violated and a Conditional Petition for Review with respect to FRAND issues. In June 2014, Microsoft Mobile Oy (“MMO”) was added as a respondent in the investigation. On August 14, 2014, the Commission determined to review in part the June 13, 2014 ID but terminated the investigation with a finding of no violation. On October 10, 2014, InterDigital filed a petition for review with the U.S. Court of Appeals for the Federal Circuit (the “Federal Circuit”), appealing certain of the adverse determinations in the Commission’s August 8, 2014 final determination including those related to the ’966 and ’847 patents. On June 2, 2015, InterDigital moved to voluntarily dismiss the Federal Circuit appeal, because, even if it were to prevail, it did not believe there would be sufficient time following the court’s decision and mandate for the USITC to complete its proceedings on remand such that the accused products would be excluded before the ’966 and ’847 patents expire in June 2016. The court granted the motion and dismissed the appeal on June 18, 2015. Related Delaware District Court Proceeding On January 2, 2013, the Company’s wholly owned subsidiaries InterDigital Communications, Inc., InterDigital Technology Corporation, IPR Licensing, Inc. and InterDigital Holdings, Inc. filed four related district court actions in the Delaware District Court against the 337-TA-868 Respondents. The proceedings against Huawei, Samsung and Nokia were subsequently dismissed, as discussed below. The remaining complaint alleges that ZTE infringes the same patents with respect to the same products alleged in the complaint filed by InterDigital in USITC Proceeding (337-TA-868). The complaint seeks a permanent injunction and compensatory damages in an amount to be determined, as well as enhanced damages based on willful infringement, and recovery of reasonable attorneys’ fees and costs. On January 31, 2013, ZTE filed its answer and counterclaims to InterDigital’s Delaware District Court complaint; ZTE asserted counterclaims for breach of contract, equitable estoppel, waiver of right to enjoin and declarations that InterDigital has not offered ZTE licenses on FRAND terms, declarations seeking the determination of FRAND terms and declarations of noninfringement, invalidity and unenforceability. In addition to the declaratory relief specified in its counterclaims, ZTE seeks specific performance of InterDigital's purported contracts with ZTE and standards-setting organizations, appropriate damages in an amount to be determined at trial, reasonable attorneys’ fees and such other relief as the court may deem appropriate. On March 21, 2013, pursuant to stipulation, the Delaware District Court granted InterDigital leave to file an amended complaint against ZTE to assert allegations of infringement of the ’244 patent. On March 22, 2013, ZTE filed its answer and counterclaims to InterDigital’s amended Delaware District Court complaint. On April 9, 2013, InterDigital filed a motion to dismiss ZTE’s counterclaims relating to its FRAND allegations. On July 12, 2013, the Delaware District Court held a hearing on InterDigital’s motion to dismiss. By order issued the same day, the Delaware District Court granted InterDigital’s motion, dismissing ZTE's counterclaims for equitable estoppel and waiver of the right to injunction or exclusionary relief with prejudice. It further dismissed the counterclaims for breach of contract and declaratory relief related to InterDigital’s FRAND commitments with leave to amend. On August 6, 2013, ZTE filed its answer and amended counterclaims for breach of contract and for declaratory judgment seeking determination of FRAND terms. The counterclaims also continue to seek declarations of noninfringement, invalidity, and unenforceability. On August 30, 2013, InterDigital filed a motion to dismiss the declaratory judgment counterclaim relating to the request for determination of FRAND terms. On May 28, 2014, the court granted InterDigital’s motion and dismissed ZTE's FRAND-related declaratory judgment counterclaim, ruling that such declaratory judgment would serve no useful purpose. On December 30, 2013, InterDigital and Huawei filed a stipulation of dismissal on account of the confidential settlement agreement and agreement to arbitrate their disputes in this action. On the

Compensation Plans and Programs

Compensation Plans and Programs	12 Months Ended
	Dec. 31, 2017
COMPENSATION PLANS AND PROGRAMS [Abstract]
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]	COMPENSATION PLANS AND PROGRAMS Compensation Programs We use a variety of compensation programs to both attract and retain employees, and to more closely align employee compensation with company performance. These programs include, but are not limited to, short-term incentive awards tied to performance goals and cash awards to inventors for filed patent applications and patent issuances, as well as stock option awards, time-based RSU awards and performance-based RSU awards under the LTCP. Our LTCP typically includes annual time-based RSU grants with a three-year vesting period, as well as annual performance-based RSU awards with a three to five-year performance period; as a result, in any one year, we are typically accounting for at least three active LTCP cycles. We issue new shares of our common stock to satisfy our obligations under the share-based components of these programs. However, our Board of Directors has the right to authorize the issuance of treasury shares to satisfy such obligations in the future. Equity Incentive Plans On June 14, 2017, our shareholders adopted and approved the 2017 Equity Incentive Plan (the "2017 Plan"), under which employees, directors and consultants can receive share-based awards such as RSUs, restricted stock and stock options as well as other stock or cash awards. From June 2009 through June 14, 2017, we granted such awards pursuant to our 2009 Stock Incentive Plan (the “2009 Plan," and, together with the 2017 Plan, the "Equity Plans"), which was adopted and approved by our shareholders on June 4, 2009, and the material terms of which were re-approved on June 12, 2014. Upon the adoption of the 2017 Plan in June 2017, the 2009 Plan was terminated and all shares remaining available for grant under the 2009 Plan were canceled. The number of shares available for issuance under the 2017 Plan is equal to 2,400,000 shares plus any shares subject to awards granted under the 2009 Plan that, on or after June 14, 2017, expire or otherwise terminate without having been exercised in full, or that are forfeited to or repurchased by us. The following table summarizes changes in the number of equity instruments available for grant (in thousands) under the Equity Plans for the current year: Available for Grant Balance at December 31, 2016 1,236 RSUs granted (a) (295 ) Options granted (25 ) Options expired and RSUs canceled 246 Balance at June 14, 2017 1,162 Remaining available shares canceled under 2009 Plan (1,162 ) Shares authorized under 2017 Plan 2,400 RSUs granted (a) (8 ) Options expired and RSUs canceled 11 Balance at December 31, 2017 2,403 (a) RSUs granted include time-based RSUs, performance-based RSUs and dividend equivalents credited. RSUs and Restricted Stock We may issue RSUs and/or shares of restricted stock to officers, employees, non-employee directors and consultants. Any cancellations of outstanding RSUs granted under the Equity Plans will increase the number of RSUs and/or shares of restricted stock remaining available for grant under the 2017 Plan. Time-based RSUs vest over periods generally ranging from 1 to 3 years from the date of the grant. Performance-based RSUs generally have a vesting period of between 3 and 5 years. During 2017 and 2016, we granted approximately 0.2 million and 0.4 million RSUs, respectively, under the Equity Plans. At December 31, 2017 and 2016, we had unrecognized compensation cost related to share-based awards of $13.6 million and $24.8 million , respectively. For grants made in 2017, 2016 and 2015 that cliff vest, we expect to amortize the associated unrecognized compensation cost at December 31, 2017 on a straight-line basis over a three-year period. Vesting of performance-based RSU awards is subject to attainment of specific goals established by the Compensation Committee of the Board of Directors. Depending upon performance against these goals, the payout range for performance-based RSU awards can be anywhere from 0 to 2 times the value of the award. Information with respect to current RSU activity is summarized as follows (in thousands, except per share amounts): Number of Unvested RSUs Weighted Average Per Share Grant Date Fair Value Balance at December 31, 2016 1,398 $ 46.65 Granted* 317 58.63 Forfeited* (22 ) 63.30 Vested* (688 ) 35.14 Balance at December 31, 2017 1,005 $ 57.95 * These numbers include less than 0.1 million RSUs credited on unvested RSU awards as dividend equivalents. Dividend equivalents accrue with respect to unvested RSU awards when and as cash dividends are paid on the Company's common stock, and vest if and when the underlying RSUs vest. Granted amounts include performance-based RSU awards at their maximum potential payout level of 200%. The total vest date fair value of the RSUs that vested in 2017, 2016 and 2015 was $56.0 million , $9.8 million and $26.3 million , respectively. The weighted average per share grant date fair value of the awards that vested in 2017, 2016 and 2015 was $35.14 , $44.08 and $41.29 , respectively. Other RSU Grants We also grant RSUs to all non-management Board members, certain consultants and, in special circumstances, management personnel outside of the LTCP. Grants of this type are supplemental to any awards granted to management personnel through the LTCP. Stock Options The 2009 Plan allowed, and the 2017 Plan allows, for the granting of incentive and non-qualified stock options, as well as other securities. The administrator of the Equity Plans, the Compensation Committee of the Board of Directors, determines the number of options to be granted, subject to certain limitations set forth in the 2017 Plan. Annually, since 2013, both incentive and non-qualified stock options have been granted pursuant to the LTCP. Under the terms of the Equity Plans, the exercise price per share of each option, other than in the event of options granted in connection with a merger or other acquisition, cannot be less than 100% of the fair market value of a share of common stock on the date of grant. Options granted under the Equity Plans are generally exercisable for a period of between 7 to 10 years from the date of grant and may vest on the grant date, another specified date or over a period of time. We also have approximately 0.1 million options outstanding under a prior stock plan that have an indefinite contractual life. Information with respect to current year stock option activity is summarized as follows (in thousands, except per share amounts): Outstanding Options Weighted Balance at December 31, 2016 515 $ 37.38 Granted 25 85.85 Canceled — — Exercised (9 ) 44.20 Balance at December 31, 2017 531 $ 39.55 The weighted average remaining contractual life of our outstanding options was 8.50 years as of December 31, 2017 . We currently have approximately 0.1 million options outstanding that have an indefinite contractual life. These options were granted between 1983 and 1986 under a prior stock plan. For purposes of calculating the weighted average remaining contractual life, these options were assigned an original life in excess of 50 years. The majority of these options have an exercise price between $9.00 and $11.63 . The total intrinsic value of stock options exercised during the years ended December 31, 2017 , 2016 and 2015 was $0.3 million , $1.5 million and $0.2 million , respectively. The total intrinsic value of our options outstanding at December 31, 2017 was $19.7 million . In 2017 , we recorded cash received from the exercise of options of approximately $0.4 million . Upon option exercise, we issued new shares of stock. At both December 31, 2017 and 2016 , we had approximately 0.5 million options outstanding that had exercise prices less than the fair market value of our stock at the respective balance sheet date. These options would have generated cash proceeds to the Company of $21.2 million and $19.4 million , respectively, if they had been fully exercised on those dates. Defined Contribution Plans We have a 401(k) plan (“Savings Plan”) wherein employees can elect to defer compensation within federal limits. We match a portion of employee contributions. Our 401(k) contribution expense was approximately $1.4 million , $1.1 million and $1.2 million for 2017 , 2016 and 2015 , respectively. At our discretion, we may also make a profit-sharing contribution to our employees’ 401(k) accounts.

Income Taxes (Notes)

Income Taxes (Notes)	12 Months Ended
	Dec. 31, 2017
INCOME TAXES: [Abstract]
Income Tax Disclosure [Text Block]	. TAXES Our income tax provision consists of the following components for 2017 , 2016 and 2015 (in thousands): 2017 2016 2015 Current Federal $ 3,656 $ 14,637 $ 42,181 State (1 ) (60 ) 415 Foreign source withholding tax 47,592 79,932 55,276 51,247 94,509 97,872 Deferred Federal 21,671 (48,086 ) (89,026 ) State (1,074 ) (557 ) 554 Foreign source withholding tax 49,832 70,925 55,221 70,429 22,282 (33,251 ) Total $ 121,676 $ 116,791 $ 64,621 The deferred tax assets and liabilities were comprised of the following components at December 31, 2017 and 2016 (in thousands): 2017 Federal State Foreign Total Net operating losses $ 1,804 $ 122,364 $ 988 $ 125,156 Deferred revenue, net 9,058 35 29,189 38,282 Stock compensation 6,643 2,293 — 8,936 Patent amortization 16,052 7 — 16,059 Depreciation (214 ) (65 ) — (279 ) Other-than-temporary impairment 379 71 — 450 Other accrued liabilities 268 (26 ) — 242 Other employee benefits 3,449 649 — 4,098 37,439 125,328 30,177 192,944 Less: valuation allowance (1,773 ) (121,155 ) (988 ) (123,916 ) Net deferred tax asset $ 35,666 $ 4,173 $ 29,189 $ 69,028 2016 Federal State Foreign Total Net operating losses $ — $ 89,162 $ 463 $ 89,625 Deferred revenue, net 60,320 288 31,686 92,294 Stock compensation 12,648 2,038 — 14,686 Patent amortization 24,145 — — 24,145 Depreciation (502 ) (70 ) — (572 ) Other accrued liabilities 4,483 321 — 4,804 Other-than-temporary impairment 558 61 — 619 Other employee benefits 2,524 275 — 2,799 104,176 92,075 32,149 228,400 Less: valuation allowance — (89,352 ) (463 ) (89,815 ) Net deferred tax asset $ 104,176 $ 2,723 $ 31,686 $ 138,585 Note: Included within the balance sheet, but not reflected in the tables are deferred tax assets primarily related to foreign withholding taxes that are expected to be paid within the next twelve months of $14.9 million and $10.9 million as of December 31, 2017 and December 31, 2016, respectively. The following is a reconciliation of income taxes at the federal statutory rate with income taxes recorded by the Company for the years ended December 31, 2017 , 2016 and 2015 (in thousands): 2017 2016 2015 Tax at U.S. statutory rate 35.0 % 35.0 % 35.0 % State tax provision — % (0.1 )% 0.5 % Change in federal and state valuation allowance 0.5 % 0.1 % — % Research and development tax credits (0.8 )% (0.5 )% (1.2 )% Uncertain tax positions (2.4 )% 2.1 % — % Permanent differences 1.0 % 0.6 % 1.2 % Domestic production activities deduction (2.0 )% (9.8 )% — % Stock compensation (4.0 )% — % — % Rate change (a) 14.6 % — % — % Other (0.3 )% 0.3 % 0.2 % Total tax provision (b) 41.6 % 27.7 % 35.7 % (a) In 2017, the inclusion of the revaluation of the deferred tax assets attributable to the Tax Reform Act signed into law in December 2017 increased the tax provision by 14.6% . (b) In 2016, the inclusion of benefits associated with domestic production activities, net of uncertain tax provisions, related to prior years reduced the tax provision by 5.6%. Income Tax Reform On December 22, 2017, the Tax Reform Act was signed into law. The Tax Reform Act significantly revised the U.S. corporate income tax regime by, among other things: lowering the U.S. corporate tax rate from 35% to 21% effective January 1, 2018; imposing a 13.125% tax rate on income that qualifies as Foreign Derived Intangible Income ("FDII"); repealing the deduction for domestic production activities; implementing a territorial tax system; and imposing a repatriation tax on deemed repatriated earnings of foreign subsidiaries. GAAP requires that the impact of tax legislation be recognized in the period in which the law was enacted. As a result of the Tax Reform Act, we recorded a tax charge of approximately $42.6 million in 2017 due to a re-measurement of deferred tax assets and liabilities, and we do not expect a material repatriation tax liability to be owed. We will continue to monitor as additional guidance is released. The tax charge represents provisional amounts and the Company’s current best estimates. Any adjustments recorded to the provisional amounts through fourth quarter 2018 will be included in net income as an adjustment to tax expense. The provisional amounts incorporate assumptions made based upon our current interpretation of the Tax Reform Act and may change as the Company receives additional clarification and implementation guidance. On a go-forward basis, we currently expect a significant portion of our income to qualify as FDII and thus be subject to the 13.125% tax rate. Valuation Allowances and Net Operating Losses We establish a valuation allowance for any portion of our deferred tax assets for which management believes it is more likely than not that we will be unable to utilize the assets to offset future taxes. We believe it is more likely than not that the majority of our state deferred tax assets will not be utilized; therefore we have maintained a near full valuation allowance against our state deferred tax assets as of December 31, 2017 . All other deferred tax assets are fully benefited. As discussed in Note 2, the Company adopted ASU 2016-09 effective January 1, 2017. Under ASU 2016-09, tax windfalls and shortfalls related to the tax effects of employee share-based compensation no longer reside within additional paid-in-capital, rather these windfalls and shortfalls are included within our income tax provision. During 2017, we realized $12.1 million of tax windfalls which was recorded as a reduction to our income tax provision. In the past, we recognized excess tax benefits associated with share-based compensation to shareholders’ equity only when realized. When assessing whether excess tax benefits relating to share-based compensation had been realized, we followed the with and without approach excluding any indirect effects of the excess tax deductions. Under the approach, excess tax benefits related to share-based compensation are not deemed to be realized until after the utilization of all other tax benefits available to the Company. During 2016 and 2015, we realized $0.6 million and $2.5 million of tax windfalls, respectively, and were recorded as a corresponding entry to additional paid-in capital. As of December 31, 2016, we had $11.9 million of state unrealized tax benefits associated with share-based compensation. These amounts were recorded on the balance sheet in 2017 when the company adopted ASU 2016-09. There was no impact to retained earnings as the amount was offset by a full valuation allowance. Uncertain Income Tax Positions As of December 31, 2017, 2016 and 2015, we had $3.3 million , $10.4 million and $1.5 million , respectively, of unrecognized tax benefits that, if recognized, would impact the Company's effective tax rate. The total amount of unrecognized tax benefits could change within the next twelve months for a number of reasons including audit settlements, tax examination activities and the recognition and measurement considerations under this guidance. During 2017, we released a reserve of $6.5 million as a result of the IRS Joint Committee issuing a letter ruling in acceptance of the refund claims associated with the domestic production activities deduction and research and development credit. Additionally, we reduced the previously established reserve for the 2016 domestic production activities deduction and research and development credit by $1.6 million . These reductions in reserves were partially offset by the establishment of a $1.0 million reserve related to the 2017 research and development and manufacturing deduction credit, as well an increase for interest and penalty on previously recognized reserves. During 2016, we established a reserve of $3.2 million related to the recognition of the 2016 research and development credit and manufacturing deduction credit. We also established a reserve of $6.3 million related to the recognition of a gross benefit for manufacturing deduction credits related to prior years and released a reserve of $0.6 million for research and development credits. The 2016 reserve was also increased for interest and penalty on previously recognized reserves. During 2015, the reserve was increased for interest and penalty on previously recognized reserves, and we also established a reserve of $0.1 million related to the recognition of the 2015 research and development credit. The following is a roll forward of our total gross unrecognized tax benefits, which if reversed would impact the effective tax rate, for the fiscal years 2015 through 2017 (in thousands): 2017 2016 2015 Balance as of January 1 $ 10,397 $ 1,469 $ 1,361 Tax positions related to current year: Additions 1,009 3,209 141 Reductions — — — Tax positions related to prior years: Additions — 6,281 — Reductions (1,610 ) — (33 ) Settlements (6,544 ) (562 ) — Lapses in statues of limitations — — — Balance as of December 31 $ 3,252 $ 10,397 $ 1,469 Our policy is to recognize interest and/or penalties related to income tax matters in income tax expense. For certain positions that related to years prior to 2017, we have recorded approximately $0.1 million of accrued interest during 2017 and 2016. The Company and its subsidiaries are subject to United States federal income tax, foreign income and withholding taxes and income taxes from multiple state jurisdictions. Our federal income tax returns for 2011 to the present are currently open and will not close until the respective statutes of limitations have expired. The statutes of limitations generally expire three years following the filing of the return or in some cases three years following the utilization or expiration of net operating loss carry forwards. The statute of limitations applicable to our open federal returns will expire at the end of 2020. The 2017 return is expected to be filed by October 16, 2018 and the statute of limitations will expire three years from the date it is filed. Specific tax treaty procedures remain open for certain jurisdictions for 2007, 2008 and 2009. Many of our subsidiaries have filed state income tax returns on a separate company basis. To the extent these subsidiaries have unexpired net operating losses, their related state income tax returns remain open. These returns have been open for varying periods, some exceeding ten years. The total amount of state net operating losses is $1.6 billion . The Company has an ongoing audit of its California tax returns for years 2012 through 2015. The U.S. Internal Revenue Service ("IRS") concluded their audit of tax years 2010 through 2012 in 2015 and the refund, related to research and development tax credits, was reviewed by the Joint Committee on Taxation, as all refund claims in excess of $5.0 million are reviewed. In February 2016, we received correspondence from the Joint Committee on Taxation confirming the results of the IRS exam with no exception. We reversed our related reserve for unrecognized tax benefits of $0.6 million in first quarter 2016. In second quarter 2016, we filed amended returns for 2011 through 2014 related to the manufacturing deduction and received notice from the IRS in third quarter 2016 that the amended years, along with the originally filed return for 2015, were open to examination. The examination concluded in second quarter 2017 and the refund claims were confirmed by the Joint Committee on Taxation in third quarter 2017. Accordingly, we adjusted our reserve for unrecognized tax benefits in the amount of $8.0 million in 2017. Foreign Taxes We pay foreign source withholding taxes on patent license royalties and state taxes when applicable. We apply foreign source withholding tax payments against our United States federal income tax obligations to the extent we have foreign source income to support these credits. In 2017 , 2016 and 2015 , we paid $46.7 million , $79.9 million and $55.3 million in foreign source withholding taxes, respectively, and applied these payments as credits against our United States federal tax obligation. Between 2007 and 2017, we paid approximately $422.3 million in foreign taxes for which we have claimed foreign tax credits against our U.S. tax obligations. Of this amount, $275.2 million relates to taxes paid to foreign governments that have tax treaties with the U.S. It is possible that as a result of tax treaty procedures, the U.S. government may reach an agreement with the related foreign governments that will result in a partial refund of foreign taxes paid with a related reduction in our foreign tax credits. Due to both foreign currency fluctuations and differences in the interest rate charged by the U.S. government compared to the interest rates, if any, used by the foreign governments, any such agreement could result in net interest expense and/or foreign currency gain or loss.

Equity Transactions (Notes)

Equity Transactions (Notes)	12 Months Ended
	Dec. 31, 2017
EQUITY TRANSACTIONS: [Abstract]
Stockholders' Equity Note Disclosure [Text Block]	EQUITY TRANSACTIONS Repurchase of Common Stock In June 2014, our Board of Directors authorized a $300 million share repurchase program (the “2014 Repurchase Program”). In June 2015, our Board of Directors authorized a $100 million increase to the program, and in September 2017, our Board of Directors authorized another $100 million increase to the program, bringing the total amount of the 2014 Repurchase Program to $500 million. The Company may repurchase shares under the 2014 Repurchase Program through open market purchases, pre-arranged trading plans or privately negotiated purchases. The table below sets forth the total number of shares repurchased and the dollar value of shares repurchased under the 2014 Repurchase Program, in thousands. 2014 Repurchase Program # of Shares Value 2017 107 $ 7,693 2016 1,304 64,685 2015 1,836 96,410 2014 3,554 152,625 Total 6,801 $ 321,413 Dividends Cash dividends on outstanding common stock declared in 2017 and 2016 were as follows (in thousands, except per share data): 2017 Per Share Total Cumulative by Fiscal Year First quarter $ 0.30 $ 10,404 $ 10,404 Second quarter 0.30 10,413 20,817 Third quarter 0.35 12,149 32,966 Fourth quarter 0.35 12,156 45,122 $ 1.30 $ 45,122 2016 First quarter $ 0.20 $ 6,923 $ 6,923 Second quarter 0.20 6,861 13,784 Third quarter 0.30 10,285 24,069 Fourth quarter 0.30 10,290 34,359 $ 1.00 $ 34,359 In September 2017, we announced that our Board of Directors had approved an increase in the Company’s quarterly cash dividend to $0.35 per share. We currently expect to continue to pay dividends comparable to our quarterly $0.35 per share cash dividend in the future; however, continued payment of cash dividends and changes in the Company's dividend policy will depend on the Company's earnings, financial condition, capital resources and capital requirements, alternative uses of capital, restrictions imposed by any existing debt, economic conditions and other factors considered relevant by our Board of Directors. Common Stock Warrants On March 5 and March 9, 2015, we sold warrants to acquire approximately 3.8 million and approximately 0.6 million shares of our common stock, respectively, subject to customary anti-dilution adjustments. As of December 31, 2017, the warrants had a strike price of approximately $88.03 per share, as adjusted. The warrants become exercisable and expire in daily tranches over a three-and-a-half-month period starting in June 2020. As consideration for the warrants issued on March 5 and March 9, 2015, we received approximately $37.3 million and approximately $5.6 million , respectively.

Selected Quarterly Results

Selected Quarterly Results	12 Months Ended
	Dec. 31, 2016
SELECTED QUARTERLY RESULTS (Unaudited) [Abstract]
Quarterly Financial Information [Text Block]	SELECTED QUARTERLY RESULTS (UNAUDITED) The table below presents quarterly data for the years ended December 31, 2017 and 2016 : First Second Third Fourth (In thousands, except per share amounts, unaudited) 2017 Revenues (a) $ 94,530 $ 135,779 $ 97,325 $ 205,304 Net income applicable to InterDigital, Inc.'s common shareholders $ 33,756 $ 52,499 $ 35,536 $ 52,502 Net income per common share — basic $ 0.98 $ 1.51 $ 1.02 $ 1.52 Net income per common share — diluted $ 0.93 $ 1.46 $ 1.00 $ 1.48 2016 Revenues (b) $ 107,764 $ 75,915 $ 208,307 $ 273,868 Net income applicable to InterDigital, Inc.'s common shareholders $ 28,071 $ 39,994 $ 104,466 $ 136,470 Net income per common share — basic $ 0.80 $ 1.16 $ 3.05 $ 3.98 Net income per common share — diluted $ 0.79 $ 1.14 $ 2.99 $ 3.85 (a) In 2017, we recognized $ 162.9 million of past patent royalties primarily attributable to the LG PLA, the recognition of a prepayment balance remaining under a patent license agreement that expired in fourth quarter 2017 and our second quarter 2017 settlement agreement with Microsoft Corporation. (b) In 2016, we recognized $ 309.7 million of past patent royalties primarily due to new patent license agreements.

Other Expense Income (Notes)

Other Expense Income (Notes)	12 Months Ended
	Dec. 31, 2017
Other Income and Other Expense Disclosure [Text Block]	12. OTHER (EXPENSE) INCOME Other expense is comprised of the following (in thousands): For the Year Ended December 31, 2017 2016 2015 Interest expense $ (17,845 ) $ (21,126 ) $ (30,417 ) Interest and investment income 8,488 3,748 3,858 Other 252 2,343 (975 ) $ (9,105 ) $ (15,035 ) $ (27,534 )

Summary of Significant Accoun20

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements [Abstract]
Consolidation, Variable Interest Entity, Policy [Policy Text Block]	In determining whether we are the primary beneficiary of a variable interest entity and therefore required to consolidate, we apply a qualitative approach that determines whether we have both the power to direct the economically significant activities of the entity and the obligation to absorb losses of, or the right to receive benefits from, the entity that could potentially be significant to that entity. These considerations impact the way we account for our existing collaborative relationships and other arrangements. We continuously assess whether we are the primary beneficiary of a variable interest entity as changes to existing relationships or future transactions may result in us consolidating or deconsolidating our partner(s) to collaborations and other arrangements. 14. VARIABLE INTEREST ENTITIES As further discussed below, we are the primary beneficiary of two variable interest entities. As of December 31, 2017, the combined book values of the assets and liabilities associated with these variable interest entities included in our Consolidated Balance Sheet were $34.4 million and $0.2 million , respectively. Assets included $23.3 million of cash and cash equivalents and $11.1 million of patents, net. As of December 31, 2016, the combined book values of the assets and liabilities associated with these variable interest entities included in our Consolidated Balance Sheet were $28.9 million and $2.3 million , respectively. Assets included $20.3 million of cash and cash equivalents and $8.0 million of patents, net. The impact of consolidating these variable interest entities on our Consolidated Statements of Income was not significant. Convida Wireless On September 26, 2015, we renewed and expanded our joint venture with Sony, Convida Wireless, to include 5G technologies. Convida Wireless was launched in 2013 to combine Sony's consumer electronics expertise with our pioneering IoT expertise to drive IoT communications and connectivity. Based on the terms of the agreement, the parties will contribute funding and resources for additional research and platform development, which we will perform. SCP IP Investment LLC, an affiliate of Stephens Inc., is a minority investor in Convida Wireless. Convida Wireless is a variable interest entity. Based on our provision of research and platform development services to Convida Wireless, we have determined that we remain the primary beneficiary for accounting purposes and will continue to consolidate Convida Wireless. For the years ended December 31, 2017, 2016 and 2015, we have allocated approximately $3.6 million , $3.5 million and $2.8 million , respectively, of Convida Wireless' net loss to noncontrolling interests held by other parties. Signal Trust for Wireless Innovation In 2013, we established the Signal Trust for Wireless Innovation ("Signal Trust"), the goal of which is to monetize a large patent portfolio related to cellular infrastructure. The more than 500 patents and patent applications transferred from InterDigital to the Signal Trust focus primarily on 3G and LTE technologies, and were developed by InterDigital's engineers and researchers over more than a decade, with a number of the innovations contributed to the worldwide standards process. InterDigital is the primary beneficiary of the Signal Trust. The distributions from the Signal Trust will support continued research related to cellular wireless technologies. A small portion of the proceeds from the Signal Trust will be used to fund, through the Signal Foundation for Wireless Innovation, scholarly analysis of intellectual property rights and the technological, commercial and creative innovations they facilitate. The Signal Trust is a variable interest entity. Based on the terms of the Trust Agreement, we have determined that we are the primary beneficiary for accounting purposes and must consolidate the Signal Trust.
Consolidation, Policy [Policy Text Block]	Principles of Consolidation The accompanying consolidated financial statements include all of our accounts and all entities in which we have a controlling interest and/or are required to be consolidated in accordance with the Generally Accepted Accounting Principles in the United States (“GAAP”). All significant intercompany accounts and transactions have been eliminated in consolidation.
Use of Estimates, Policy [Policy Text Block]	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from these estimates. If different assumptions were made or different conditions had existed, our financial results could have been materially different.
Cash and Cash Equivalents, Policy [Policy Text Block]	Cash and Cash Equivalents We classify all highly liquid investment securities with original maturities of three months or less at date of purchase as cash equivalents. Our investments are comprised of mutual and exchange traded funds, commercial paper, United States and municipal government obligations and corporate securities. Management determines the appropriate classification of our investments at the time of acquisition and re-evaluates such determination at each balance sheet date. Cash and cash equivalents at December 31, 2017 and 2016 consisted of the following (in thousands): December 31, 2017 2016 Money market and demand accounts $ 417,348 $ 404,074 Commercial paper 15,666 — $ 433,014 $ 404,074
Marketable Securities, Available-for-sale Securities, Policy [Policy Text Block]	Marketable Securities At December 31, 2017 and 2016 , all marketable securities have been classified as available-for-sale and are carried at fair value, with unrealized gains and losses reported net-of-tax as a separate component of shareholders’ equity. Substantially all of our investments are investment grade government and corporate debt securities that have maturities of less than 3 years, and we have both the ability and intent to hold the investments until maturity. During both 2016 and 2015, we recorded other-than-temporary impairments of approximately $0.2 million . The gross realized gains and losses on sales of marketable securities were not significant during the years ended December 31, 2017, 2016 and 2015. Marketable securities as of December 31, 2017 and 2016 consisted of the following (in thousands): December 31, 2017 Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Available-for-sale securities Commercial paper 66,132 — — 66,132 U.S. government securities 513,645 — (2,613 ) 511,032 Corporate bonds, asset backed and other securities 164,075 35 (627 ) 163,483 Total available-for-sale securities $ 743,852 $ 35 $ (3,240 ) $ 740,647 Reported in: Cash and cash equivalents $ 15,666 Short-term investments 724,981 Total marketable securities $ 740,647 December 31, 2016 Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Available-for-sale securities Commercial paper 113,490 — — 113,490 U.S. government securities 224,583 9 (262 ) 224,330 Corporate bonds, asset backed and other securities 211,406 28 (567 ) 210,867 Total available-for-sale securities $ 549,479 $ 37 $ (829 ) $ 548,687 Reported in: Cash and cash equivalents $ — Short-term investments 548,687 Total marketable securities $ 548,687 At December 31, 2017 and 2016 , $345.0 million and $404.8 million , respectively, of our short-term investments had contractual maturities within one year. The remaining portions of our short-term investments had contractual maturities primarily within two to five years
Fair Value of Financial Instruments, Policy [Policy Text Block]	Concentration of Credit Risk and Fair Value of Financial Instruments Financial instruments that potentially subject us to concentration of credit risk consist primarily of cash equivalents, short-term investments and accounts receivable. We place our cash equivalents and short-term investments only in highly rated financial instruments and in United States government instruments. Our accounts receivable are derived principally from patent license and technology solutions agreements. At December 31, 2017 and 2016, three and four licensees comprised 96% and 91% , respectively, of our accounts receivable balance. We perform ongoing credit evaluations of our licensees, who generally include large, multinational, wireless telecommunications equipment manufacturers. We believe that the book values of our financial instruments approximate their fair values. Fair Value Measurements We use various valuation techniques and assumptions when measuring the fair value of our assets and liabilities. We utilize market data or assumptions that market participants would use in pricing the asset or liability, including assumptions about risk and the risks inherent in the inputs to the valuation technique. This guidance established a hierarchy that prioritizes fair value measurements based on the types of input used for the various valuation techniques (market approach, income approach and cost approach). The levels of the hierarchy are described below: Level 1 Inputs — Level 1 includes financial instruments for which quoted market prices for identical instruments are available in active markets. Level 2 Inputs — Level 2 includes financial instruments for which there are inputs other than quoted prices included within Level 1 that are observable for the instrument such as quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets with insufficient volume or infrequent transactions (less active markets) or model-driven valuations in which significant inputs are observable or can be derived principally from, or corroborated by, observable market data, including market interest rate curves, referenced credit spreads and pre-payment rates. Level 3 Inputs — Level 3 includes financial instruments for which fair value is derived from valuation techniques including pricing models and discounted cash flow models in which one or more significant inputs are unobservable, including the company’s own assumptions. The pricing models incorporate transaction details such as contractual terms, maturity and, in certain instances, timing and amount of future cash flows, as well as assumptions related to liquidity and credit valuation adjustments of marketplace participants. Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of financial assets and financial liabilities and their placement within the fair value hierarchy. We use quoted market prices for similar assets to estimate the fair value of our Level 2 investments. Our financial assets are included within short-term investments on our consolidated balance sheets, unless otherwise indicated. Our financial assets that are accounted for at fair value on a recurring basis are presented in the tables below as of December 31, 2017 and December 31, 2016 (in thousands): Fair Value as of December 31, 2017 Level 1 Level 2 Level 3 Total Assets: Money market and demand accounts (a) $ 417,348 $ — $ — $ 417,348 Commercial paper (b) — 66,132 — 66,132 U.S. government securities — 511,032 — 511,032 Corporate bonds, asset backed and other securities — 163,483 — 163,483 $ 417,348 $ 740,647 $ — $ 1,157,995 _______________ (a) Included within cash and cash equivalents. (b) Includes $15.7 million of commercial paper that is included within cash and cash equivalents. Fair Value as of December 31, 2016 Level 1 Level 2 Level 3 Total Assets: Money market and demand accounts (a) $ 404,074 $ — $ — $ 404,074 Commercial paper — 113,490 — 113,490 U.S. government securities — 224,330 — 224,330 Corporate bonds and asset backed securities — 210,867 — 210,867 $ 404,074 $ 548,687 $ — $ 952,761 _______________ (a) Included within cash and cash equivalents. The principal amount, carrying value and related estimated fair value of the Company's long-term debt reported in the Consolidated Balance Sheets as of December 31, 2017 and December 31, 2016 are as follows (in thousands): December 31, 2017 December 31, 2016 Principal Amount Carrying Value Fair Value Principal Amount Carrying Fair Value Total Long-Term Debt $ 316,000 $ 285,126 $ 377,029 $ 316,000 $ 272,021 $ 428,575 The aggregate fair value of the principal amount of the long-term debt (Level 2 Notes as defined in Note 6 " Obligations ") was calculated using inputs such as actual trade data, benchmark yields, broker/dealer quotes and other similar data, which were obtained from independent pricing vendors, quoted market prices or other sources. As discussed in Note 3, "Significant Agreements," we acquired patents associated with a patent license agreement signed during fourth quarter 2017. We have recorded these patents based on their total estimated fair value of $19.7 million and will amortize them over their estimated useful lives. Additionally, as previously disclosed, during third quarter 2016, we entered into a multi-year, worldwide, non-exclusive, royalty-bearing patent license agreement with Huawei. A portion of the consideration for the agreement was in the form of patents from Huawei. We received the first portion of the patents as of September 30, 2016, and the remaining patents during third quarter 2017. We have recorded these additional patents based on their total estimated fair value of $12.8 million and will amortize them over their estimated useful lives. We estimated the fair value of the patents in these transactions through a combination of a discounted cash flow analysis (the income approach) and an analysis of comparable market transactions (the market approach). For the income approach, the inputs and assumptions used to develop these estimates were based on a market participant perspective and included estimates of projected royalties, discount rates, economic lives and income tax rates, among others. For the market approach, judgment was applied as to which market transactions were most comparable to the transaction.
Property, Plant and Equipment, Policy [Policy Text Block]	Property and Equipment Property and equipment are stated at cost. Depreciation and amortization of property and equipment are provided using the straight-line method. The estimated useful lives for computer equipment, computer software, engineering and test equipment and furniture and fixtures are generally three to five years. Leasehold improvements are amortized over the lesser of their estimated useful lives or their respective lease terms, which are generally five to ten years. Buildings are being depreciated over twenty-five years. Expenditures for major improvements and betterments are capitalized, while minor repairs and maintenance are charged to expense as incurred. Leases meeting certain capital lease criteria are capitalized and the net present value of the related lease payments is recorded as a liability. Amortization of capital leased assets is recorded using the straight-line method over the lesser of the estimated useful lives or the lease terms. Upon the retirement or disposition of property, plant and equipment, the related cost and accumulated depreciation or amortization are removed, and a gain or loss is recorded.
Internal Use Software, Policy [Policy Text Block]	Internal-Use Software Costs We capitalize costs associated with software developed for internal use that are incurred during the software development stage. Such costs are limited to expenses incurred after management authorizes and commits to a computer software project, believes that it is more likely than not that the project will be completed, the software will be used to perform the intended function with an estimated service life of two years or more, and the completion of conceptual formulation, design and testing of possible software project alternatives (the preliminary design stage). Costs incurred after final acceptance testing has been successfully completed are expensed. Capitalized computer software costs are amortized over their estimated useful life of three years. All computer software costs capitalized to date relate to the purchase, development and implementation of engineering, accounting and other enterprise software.
Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block]	Other-than-Temporary Impairments We review our investment portfolio during each reporting period to determine whether there are identified events or circumstances that would indicate there is a decline in the fair value that is considered to be other-than-temporary. For non-public investments, if there are no identified events or circumstances that would have a significant adverse effect on the fair value of the investment, then the fair value is not estimated. If an investment is deemed to have experienced an other-than-temporary decline below its cost basis, we reduce the carrying amount of the investment to its quoted or estimated fair value, as applicable, and establish a new cost basis for the investment. We charge the impairment to the Other Expense (Net) line of our Consolidated Statements of Income. Impairment of Long-Lived Assets We evaluate long-lived assets for impairment when factors indicate that the carrying value of an asset may not be recoverable. When factors indicate that such assets should be evaluated for possible impairment, we review whether we will be able to realize our long-lived assets by analyzing the projected undiscounted cash flows in measuring whether the asset is recoverable. We recorded approximately $0.2 million of long-lived asset impairments in 2015. We did not have any long-lived asset impairments in 2017 or 2016.
Equity and Cost Method Investments, Policy [Policy Text Block]	Investments in Other Entities We may make strategic investments in companies that have developed or are developing technologies that are complementary to our business. We account for our investments using either the cost or equity method of accounting. Under the cost method, we do not adjust our investment balance when the investee reports profit or loss but monitor the investment for an other-than-temporary decline in value. On a quarterly basis, we monitor our investment’s financial position and performance to assess whether there are any triggering events or indicators present that would be indicative of an other-than-temporary impairment of our investment. When assessing whether an other-than-temporary decline in value has occurred, we consider such factors as the valuation placed on the investee in subsequent rounds of financing, the performance of the investee relative to its own performance targets and business plan, and the investee’s revenue and cost trends, liquidity and cash position, including its cash burn rate, and updated forecasts. Under the equity method of accounting, we initially record our investment in the stock of an investee at cost, and adjust the carrying amount of the investment to recognize our share of the earnings or losses of the investee after the date of acquisition. The amount of the adjustment is included in the determination of net income, and such amount reflects adjustments similar to those made in preparing consolidated statements including adjustments to eliminate intercompany gains and losses, and to amortize, if appropriate, any difference between our cost and underlying equity in net assets of the investee at the date of investment. The investment is also adjusted to reflect our share of changes in the investee’s capital. Dividends received from an investee reduce the carrying amount of the investment. When there are a series of operating losses by the investee or when other factors indicate that a decrease in value of the investment has occurred which is other than temporary, we recognize an impairment equal to the difference between the fair value and the carrying amount of our investment. The carrying costs of our investments are included within Other Non-Current Assets on our Consolidated Balance Sheets. During 2017 and 2016, we made investments in other entities for $4.6 million , and $2.0 million , respectively. Due to the fact that we do not have significant influence over any of these entities, we are accounting for these investments using the cost method of accounting. The carrying value of our investments in other entities measured at cost as of December 31, 2017 and 2016 was $19.2 million and $14.6 million , respectively.
Intangible Assets, Finite-Lived, Policy [Policy Text Block]	Patents We capitalize external costs, such as filing fees and associated attorney fees, incurred to obtain issued patents and patent license rights. We expense costs associated with maintaining and defending patents subsequent to their issuance in the period incurred. We amortize capitalized patent costs for internally generated patents on a straight-line basis over ten years, which represents the estimated useful lives of the patents. The ten-year estimated useful life for internally generated patents is based on our assessment of such factors as: the integrated nature of the portfolios being licensed, the overall makeup of the portfolio over time, and the length of license agreements for such patents. The estimated useful lives of acquired patents and patent rights, however, have been and will continue to be based on a separate analysis related to each acquisition and may differ from the estimated useful lives of internally generated patents. The average estimated useful life of acquired patents is 9.8 years. We assess the potential impairment to all capitalized net patent costs when events or changes in circumstances indicate that the carrying amount of our patent portfolio may not be recoverable. At December 31, 2017 and 2016, patents consisted of the following (in thousands, except for useful life data): December 31, 2017 2016 Weighted average estimated useful life (years) 10.0 9.9 Gross patents $ 660,886 $ 593,309 Accumulated amortization (335,478 ) (282,541 ) Patents, net $ 325,408 $ 310,768 Amortization expense related to capitalized patent costs was $52.9 million , $48.6 million and $44.0 million in 2017 , 2016 and 2015 , respectively. These amounts are recorded within the Patent administration and licensing line of our Consolidated Statements of Income. The estimated aggregate amortization expense for the next five years related to our patents balance as of December 31, 2017 is as follows (in thousands): 2018 $ 53,547 2019 50,672 2020 45,871 2021 41,272 2022 38,654
Goodwill and Intangible Assets, Intangible Assets, Indefinite-Lived, Policy [Policy Text Block]	The Company acquired goodwill during 2016 as a result of the acquisition of Hillcrest Labs. Refer to Note 15, " Business Combinations ," for more information regarding this transaction. The carrying value of goodwill at December 31, 2017 and 2016 was $16.0 million and $16.2 million , respectively. These amounts are included in "Other Non-Current Assets" on the Consolidated Balance Sheets. No impairments were recorded during 2017 as a result of our annual goodwill assessment. Other Intangible Assets We capitalize the cost of technology solutions and platforms we acquire or license from third parties when they have a future benefit and the development of these solutions and platforms is substantially complete at the time they are acquired or licensed. Intangible assets consist of acquired patents, existing technology, and trade names. Refer to the above Patents section for more information on acquired patents and existing technology. Our intangible assets are amortized on a straight-line basis over their estimated useful lives, ranging from 9 to 10 years. We make judgments about the recoverability of purchased finite-lived intangible assets whenever facts and circumstances indicate that the useful life is shorter than originally estimated or that the carrying amount of assets may not be recoverable. If such facts and circumstances exist, we assess recoverability by comparing the projected undiscounted net cash flows associated with the related asset or group of assets over their remaining lives against their respective carrying amounts. Impairments, if any, are based on the excess of the carrying amount over the fair value of those assets. If the useful life is shorter than originally estimated, we would accelerate the rate of amortization and amortize the remaining carrying value over the new shorter useful life. Intangible assets excluding patents consisted of the following (in thousands): December 31, 2017 December 31, 2016 Average Life (Years) Gross Assets Accumulated Amortization Net Gross Assets Accumulated Amortization Net Trade Names 9 $ 600 $ (67 ) $ 533 $ 600 $ — $ 600 Customer Relationships 10 1,700 (170 ) 1,530 1,700 — 1,700 $ 2,300 $ (237 ) $ 2,063 (a) $ 2,300 $ — $ 2,300 (a) These amounts are included in "Other Non-Current Assets" on the Consolidated Balance Sheets. Estimated future amortization expense of these intangible assets is as follows (in thousands): 2018 $ 237 2019 237 2020 237 2021 237 2022 237 Thereafter 878 $ 2,063
Revenue Recognition, Policy [Policy Text Block]	Revenue Recognition The discussion that follows below is a description of our revenue recognition practices in effect as of December 31, 2017. As discussed in more detail below under “ New Accounting Guidance, " the FASB issued guidance on revenue from contracts with customers that superseded most revenue recognition guidance in effect as of year-end 2017, including industry-specific guidance, which is effective for the Company January 1, 2018. We derive the vast majority of our revenue from patent licensing. The timing and amount of revenue recognized from each licensee depends upon a variety of factors, including the specific terms of each agreement and the nature of the deliverables and obligations. Such agreements are often complex and include multiple elements. These agreements can include, without limitation, elements related to the settlement of past patent infringement liabilities, up-front and non-refundable license fees for the use of patents and/or know-how, patent and/or know-how licensing royalties on covered products sold by licensees, cross-licensing terms between us and other parties, the compensation structure and ownership of intellectual property rights associated with contractual technology development arrangements, advanced payments and fees for service arrangements and settlement of intellectual property enforcement. For agreements entered into or materially modified prior to 2011, due to the inherent difficulty in establishing reliable, verifiable, and objectively determinable evidence of the fair value of the separate elements of these agreements, the total revenue resulting from such agreements has often been recognized over the performance period. Since January 2011, we have accounted for all new or materially modified agreements under the FASB revenue recognition guidance, "Revenue Arrangements with Multiple Deliverables." This guidance requires consideration to be allocated to each element of an agreement that has standalone value using the relative fair value method. In other circumstances, such as those agreements involving consideration for past and expected future patent royalty obligations, after consideration of the particular facts and circumstances, the appropriate recording of revenue between periods may require the use of judgment. In all cases, revenue is only recognized after all of the following criteria are met: (1) written agreements have been executed; (2) delivery of technology or intellectual property rights has occurred or services have been rendered; (3) fees are fixed or determinable; and (4) collectibility of fees is reasonably assured. We establish a receivable for payments expected to be received within twelve months from the balance sheet date based on the terms in the license. Our reporting of such payments often results in an increase to both accounts receivable and deferred revenue. Deferred revenue associated with fixed-fee royalty payments is classified on the balance sheet as short-term when it is scheduled to be amortized within twelve months from the balance sheet date. All other deferred revenue is classified as long-term, as amounts to be recognized over the next twelve months are not known. Patent License Agreements Upon signing a patent license agreement, we provide the licensee permission to use our patented inventions in specific applications. We account for patent license agreements in accordance with the guidance for revenue arrangements with multiple deliverables. We have elected to utilize the leased-based model for revenue recognition, with revenue being recognized over the expected period of benefit to the licensee. Under our patent license agreements, we typically receive one or a combination of the following forms of payment as consideration for permitting our licensees to use our patented inventions in their applications and products: Consideration for Past Patent Royalties: Consideration related to a licensee’s product sales from prior periods may result from a negotiated agreement with a licensee that utilized our patented inventions prior to signing a patent license agreement with us or from the resolution of a disagreement or arbitration with a licensee over the specific terms of an existing license agreement. We may also receive consideration for past patent royalties in connection with the settlement of patent litigation where there was no prior patent license agreement. In each of these cases, we record the consideration as revenue when we have obtained a signed agreement, identified a fixed or determinable price and determined that collectibility is reasonably assured. Fixed-Fee Royalty Payments: These are up-front, non-refundable royalty payments that fulfill the licensee’s obligations to us under a patent license agreement for a specified time period or for the term of the agreement for specified products, under certain patents or patent claims, for sales in certain countries, or a combination thereof — in each case for a specified time period (including for the life of the patents licensed under the agreement). We recognize revenues related to Fixed-Fee Royalty Payments on a straight-line basis over the effective term of the license. We utilize the straight-line method because we cannot reliably predict in which periods, within the term of a license, the licensee will benefit from the use of our patented inventions. Prepayments: These are up-front, non-refundable royalty payments towards a licensee’s future obligations to us related to its expected sales of covered products in future periods. Our licensees’ obligations to pay royalties typically extend beyond the exhaustion of their Prepayment balance. Once a licensee exhausts its Prepayment balance, we may provide them with the opportunity to make another Prepayment toward future sales or it will be required to make Current Royalty Payments. Current Royalty Payments: These are royalty payments covering a licensee’s obligations to us related to its sales of covered products in the current contractual reporting period. Licensees that either owe us Current Royalty Payments or have Prepayment balances are obligated to provide us with quarterly royalty reports that summarize their sales of covered products and their related royalty obligations to us. We typically receive these royalty reports subsequent to the period in which our licensees’ underlying sales occurred. As a result, it is impractical for us to recognize revenue in the period in which the underlying sales occur, and, in most cases, we recognize revenue in the period in which the royalty report is received and other revenue recognition criteria are met due to the fact that without royalty reports from our licensees, our visibility into our licensees’ sales is very limited. When a licensee is required to gross-up their royalty payment to cover applicable foreign withholding tax requirements, the additional consideration is recorded in revenue. The exhaustion of Prepayments and Current Royalty Payments are often calculated based on related per-unit sales of covered products. From time to time, licensees will not report revenues in the proper period, most often due to legal disputes. When this occurs, the timing and comparability of royalty revenue could be affected. In cases where we receive objective, verifiable evidence that a licensee has discontinued sales of products covered under a patent license agreement with us, we recognize any related deferred revenue balance in the period that we receive such evidence. Patent Sales Our business strategy of monetizing our intellectual property includes the sale of select patent assets. As patent sales executed under this strategy represent a component of our ongoing major or central operations and activities, we will record the related proceeds as revenue. We will recognize the revenue when there is persuasive evidence of a sales arrangement, fees are fixed or determinable, delivery has occurred and collectibility is reasonably assured. These requirements are generally fulfilled upon closing of the patent sale transaction. Technology Solutions Technology solutions revenue consists primarily of revenue from royalty payments. We recognize revenue from royalty payments using the same methods described above under our policy for recognizing revenue from patent license agreements. Technology solutions revenues also consist of revenues from software licenses, engineering services and product sales. Software license revenues are recognized in accordance with the original and revised guidance for software revenue recognition. When the arrangement with a customer includes significant production, modification, or customization of the software, we recognize the related revenue using the percentage-of-completion method in accordance with the accounting guidance for construction-type and certain production-type contracts. Under this method, revenue and profit are recognized throughout the term of the contract, based on actual labor costs incurred to date as a percentage of the total estimated labor costs related to the contract. Changes in estimates for revenues, costs and profits are recognized in the period in which they are determinable. When such estimates indicate that costs will exceed future revenues and a loss on the contract exists, a provision for the entire loss is recognized at that time. We recognize revenues associated with engineering service arrangements that are outside the scope of the accounting guidance for construction-type and certain production-type contracts on a straight-line basis, unless evidence suggests that the revenue is earned in a different pattern, over the contractual term of the arrangement or the expected period during which those specified services will be performed, whichever is longer. In such cases we often recognize revenue using proportional performance and measure the progress of our performance based on the relationship between incurred labor hours and total estimated labor hours or other measures of progress, if available. Our most significant cost has been labor and we believe both labor hours and labor cost provide a measure of the progress of our services. The effect of changes to total estimated contract costs is recognized in the period in which such changes are determined. We recognize revenues associated with product sales in the period in which the sales of the underlying units occur.
Deferred Charges, Policy [Policy Text Block]	Deferred Charges From time to time, we use sales agents to assist us in our licensing and/or patent sale activities. In such cases, we may pay a commission. The commission rate varies from agreement to agreement. Commissions are normally paid shortly after our receipt of cash payments associated with the patent license or patent sale agreements. We defer recognition of commission expense related to both prepayments and fixed-fee royalty payments and amortize these expenses in proportion to our recognition of the related revenue. In each of 2017 , 2016 and 2015 , we paid cash commissions of less than $0.3 million . Incremental direct costs incurred related to an acquisition or origination of a customer contract in a transaction that results in the deferral of revenue may be either expensed as incurred or capitalized. The only eligible costs for deferral are those costs directly related to a particular revenue arrangement. We capitalize those direct costs incurred for the acquisition of a contract through the date of signing, and amortize them on a straight-line basis over the life of the patent license agreement. There were no direct contract origination costs incurred during 2017, 2016 or 2015. Incremental direct costs incurred related to a debt financing transaction may be capitalized. In connection with our offering of the 2020 Notes, discussed in detail within Note 6, " Obligations" , we incurred directly related costs. The initial purchasers' transaction fees and related offering expenses were allocated to the liability and equity components of the debt in proportion to the allocation of proceeds and accounted for as debt issuance costs. The debt issuance costs allocated to the liability component of the debt were capitalized as deferred financing costs and recorded as a direct reduction of the debt. These costs are being amortized to interest expense over the term of the debt using the effective interest method. The costs allocated to the equity component of the debt were recorded as a reduction of the equity component of the debt. There were no debt issuance costs incurred in 2017 or 2016. Deferred charges are recorded in our Consolidated Balance Sheets within the following captions (in thousands): December 31, 2017 2016 Prepaid and other current assets Deferred commission expense $ 59 $ 187 Other non-current assets Deferred commission expense 48 181 Long-term debt (including current portion of long-term debt) Deferred financing costs 3,011 4,401 Commission expense was approximately $0.2 million , $0.4 million and $0.6 million in 2017 , 2016 and 2015 , respectively. Commission expense is included within the Patent administration and licensing line of our Consolidated Statements of Income. Deferred financing expense was $1.4 million , $1.7 million and $2.5 million in 2017 , 2016 and 2015 , respectively. Deferred financing expense is included within the Other Expense (Net) line of our Consolidated Statements of Income.
Research and Development Expense, Policy [Policy Text Block]	Research and Development Research and development expenditures are expensed in the period incurred, except certain software development costs that are capitalized between the point in time that technological feasibility of the software is established and when the product is available for general release to customers. We did not have any capitalized software costs related to research and development in any period presented. Research, development and other related costs were approximately $70.7 million , $68.7 million and $72.7 million in 2017 , 2016 and 2015 , respectively.
Compensation Related Costs, Policy [Policy Text Block]	Compensation Programs We use a variety of compensation programs to both attract and retain employees, and to more closely align employee compensation with company performance. These programs include, but are not limited to, short-term incentive awards tied to performance goals and cash awards to inventors for filed patent applications and patent issuances, as well as stock option awards, time-based restricted stock unit (“RSU”) awards and performance-based awards under our long-term compensation program ("LTCP"). Our LTCP typically includes annual RSU grants with three- to five-year vesting periods; as a result, in any one year, we are typically accounting for at least three active LTCP cycles. We account for compensation costs associated with share-based transactions based on the fair value of the instruments issued. The estimated value of stock options includes assumptions around expected life, stock volatility and dividends. The expected life of our stock option awards are based on the simplified method as prescribed by Staff Accounting Bulletin Topic 14. In all periods, our policy has been to set the value of RSUs and restricted stock awards equal to the value of our underlying common stock on the date of measurement. For grants with graded vesting, we amortize the associated unrecognized compensation cost using an accelerated method. For grants that cliff vest, we amortize the associated unrecognized compensation cost on a straight-line basis over their vesting term.
Income Tax, Policy [Policy Text Block]	Income Taxes The Tax Reform Act was signed into law on December 22, 2017. Pursuant to the Securities and Exchange Commission Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act ("SAB 118"), given the amount and complexity of the changes in tax law resulting from the Tax Reform Act, we have not yet finalized the accounting for the income tax effects of the Tax Reform Act. This includes the re-measurement of deferred taxes and transition tax on unrepatriated foreign earnings. Furthermore, we are in the process of analyzing the effects of new taxes due on certain foreign income, such as GILTI (global intangible low-taxed income), BEAT (base-erosion anti-abuse tax), FDII (foreign-derived intangible income) and limitations on interest expense deductions (if certain conditions apply) that are effective starting in fiscal 2018, and other provisions of the Tax Reform Act. As a result of the Tax Reform Act, we recorded a tax charge of approximately $42.6 million in 2017 primarily due to a re-measurement of deferred tax assets and liabilities, and we do not expect a material repatriation tax liability to be owed. The impact of the Tax Reform Act may differ from this estimate during the one-year measurement period due to, among other things, further refinement of the Company’s calculations, changes in interpretations and assumptions the Company has made, guidance that may be issued and actions the Company may take as a result of the Tax Reform Act. Income taxes are accounted for under the asset and liability method. Under this method, deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases, and operating loss and tax credit carry forwards. Deferred tax assets and liabilities are measured using enacted tax rates in effect for the year in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the Consolidated Statement of Income in the period in which the change was enacted. A valuation allowance is recorded to reduce the carrying amounts of deferred tax assets if management has determined that it is more likely than not that such assets will not be realized. In addition, the calculation of tax liabilities involves significant judgment in estimating the impact of uncertainties in the application of complex tax laws. We are subject to examinations by the U.S. Internal Revenue Service (“IRS”) and other taxing jurisdictions on various tax matters, including challenges to various positions we assert in our filings. In the event that the IRS or another taxing jurisdiction levies an assessment in the future, it is possible the assessment could have a material adverse effect on our consolidated financial condition or results of operations. The financial statement recognition of the benefit for a tax position is dependent upon the benefit being more likely than not to be sustainable upon audit by the applicable tax authority. If this threshold is met, the tax benefit is then measured and recognized at the largest amount that is greater than 50 percent likely of being realized upon ultimate settlement. In the event that the IRS or another taxing jurisdiction levies an assessment in the future, it is possible the assessment could have a material adverse effect on our consolidated financial condition or results of operations. Between 2006 and 2017, we paid approximately $422.3 million in foreign taxes for which we have claimed foreign tax credits against our U.S. tax obligations. Of this amount, $275.2 million relates to taxes paid to foreign governments that have tax treaties with the U.S. It is possible that as a result of tax treaty procedures, the U.S. government may reach an agreement with the related foreign governments that will result in a partial refund of foreign taxes paid with a related reduction in our foreign tax credits. Due to both foreign currency fluctuations and differences in the interest rate charged by the U.S. government compared to the interest rates, if any, used by the foreign governments, any such agreement could result in net interest expense and/or foreign currency gain or loss. During 2017 and 2016, we recorded an estimated benefit for domestic production activities deduction of $5.1 million and $8.3 million, respectively, net of any unrecognized tax benefits. Additionally, we included an estimated benefit for research and development credits of $2.3 million, $2.1 million and $2.1 million, net of any unrecognized tax benefits, in 2017, 2016 and 2015, respectively. During 2016, we completed a study for certain domestic production activities for the periods from 2010 to 2015 and amended our United States federal income tax returns for the periods from 2011 through 2014 to claim deductions related to domestic production activities for those periods. After all periods were amended and the 2015 federal income tax return was filed, we recognized a net benefit after consideration of any unrecognized tax benefits from the deductions in the amount of $23.6 million. In 2015, the IRS concluded their audit of tax years 2010 through 2012 of the refund related to research and development tax credits, and upon completion of the review by the Joint Committee on Taxation, we reversed our related reserve for unrecognized tax benefits of $0.6 million. During 2016, we filed amended returns for 2011 through 2014 related to the manufacturing deduction and received notice from the IRS in 2016 that the amended years, along with the originally filed return for 2015, were open to examination. The examination concluded and the refund claims were confirmed by the Joint Committee on Taxation in 2017. We decreased our reserve for unrecognized tax benefits in the amount of $8.0 million in 2017.
Earnings Per Share, Policy [Policy Text Block]	Net Income Per Common Share Basic Earnings Per Share ("EPS") is calculated by dividing net income available to common shareholders by the weighted-average number of common shares outstanding for the period. Diluted EPS reflects the potential dilution that could occur if options or other securities with features that could result in the issuance of common stock were exercised or converted to common stock. The following table reconciles the numerator and the denominator of the basic and diluted net income per share computation (in thousands, except for per share data): For the Year Ended December 31, 2017 2016 2015 Basic Diluted Basic Diluted Basic Diluted Numerator: Net income applicable to common shareholders $ 174,293 $ 174,293 $ 309,001 $ 309,001 $ 119,225 $ 119,225 Denominator: Weighted-average shares outstanding: Basic 34,605 34,605 34,526 34,526 36,048 36,048 Dilutive effect of stock options, RSUs and convertible securities 1,174 663 415 Weighted-average shares outstanding: Diluted 35,779 35,189 36,463 Earnings Per Share: Net income: Basic $ 5.04 5.04 $ 8.95 8.95 $ 3.31 3.31 Dilutive effect of stock options, RSUs and convertible securities (0.17 ) (0.17 ) (0.04 ) Net income: Diluted $ 4.87 $ 8.78 $ 3.27 Certain shares of common stock issuable upon the exercise or conversion of certain securities have been excluded from our computation of earnings per share because the strike price or conversion rate, as applicable, of such securities was greater than the average market price of our common stock for the years ended December 31, 2017 , 2016 and 2015 , as applicable, and, as a result, the effect of such exercise or conversion would have been anti-dilutive. Set forth below are the securities and the weighted average number of shares of common stock underlying such securities that were excluded from our computation of earnings per share for the periods presented (in thousands): For the Year Ended December 31, 2017 2016 2015 Restricted stock units and stock options 19 110 211 Convertible securities — 4,366 7,656 Warrants — 6,534 7,656 Total 19 11,010 15,523
New Accounting Pronouncement or Change in Accounting Principle, Description	New Accounting Guidance Accounting Standards Update: Stock Compensation In March 2016, the Financial Accounting Standards Board (the "FASB") issued ASU No. 2016-09, "Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting." ASU 2016-09 simplifies several aspects of the accounting for employee share-based payment transactions for both public and nonpublic entities, including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification in the statement of cash flows. We applied the standard beginning in first quarter 2017. Certain elements of our accounting for compensation costs associated with share-based transactions changed upon adoption of ASU 2016-09. We no longer account for these costs net of estimated award forfeitures. Instead, we adjust expense recognized to date in the event of canceled awards as they occur. The elimination of estimated forfeitures did not have a material impact on our financial statements for 2017. Additionally, tax windfalls and shortfalls related to the tax effects of employee share-based compensation no longer reside within additional paid-in-capital. Rather, these windfalls and shortfalls are included in our tax provision. We also adjusted our disclosures included within our condensed consolidated statements of cash flows. Tax windfalls and shortfalls related to employee share-based compensation awards are included within operating activities on a prospective basis and cash paid to tax authorities for shares withheld is included within financing activities retrospectively. Although these changes have no impact on the amount of share-based compensation expense we ultimately recognize, the inclusion of windfalls and shortfalls in the tax provision could increase our earnings volatility between periods. In May 2017, the FASB issued ASU 2017-09, "Stock Compensation (Topic 718): Scope of Modification Accounting." ASU 2017-09 provides clarity and reduces complexity in applying the guidance in Topic 718 to a change to the terms or conditions of a share-based payment award. We adopted this guidance early, in second quarter 2017, and it had no immediate impact on our consolidated financial statements . Accounting Standards Update: Revenue Recognition In May 2014, the FASB issued guidance on revenue from contracts with customers that superseded most revenue recognition guidance in effect at December 31, 2017, including industry-specific guidance. The underlying principle is that an entity will recognize revenue to depict the transfer of goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services. The guidance also requires enhanced disclosures regarding the nature, amount, timing and uncertainty of revenue and cash flows arising from an entity’s contracts with customers. The guidance is effective for the interim and annual periods beginning on or after December 15, 2017. The guidance permits the use of either a retrospective or cumulative effect transition method. The new guidance will affect our recognition of revenue from both our fixed-fee and per-unit license agreements beginning in first quarter 2018. For accounting purposes under this new guidance, we will separate our fixed-fee license agreements into two categories: (i) those agreements that provide rights, over the term of the license, to future technologies that are highly interdependent or highly interrelated to the technologies provided at the inception of the agreement (“Dynamic Fixed-Fee Agreements”) and (ii) those agreements that do not provide for rights to such future technologies (“Static Fixed-Fee Agreements”). Under our current accounting practices, after the fair value allocation between the past and future components of the agreement, we recognize the future components of revenue from all fixed-fee license agreements on a straight-line basis over the term of the related license agreement. Upon adoption of the new guidance, we expect to continue to recognize revenue from Dynamic Fixed-Fee Agreements on a straight-line basis over the term of the related license agreement, while we expect to recognize most or all of the revenue from Static Fixed-Fee Agreements in the quarter the license agreement is signed. We will not recognize any revenue post adoption from Static Fixed-Fee Agreements already in existence at the time the guidance is adopted. Based on our preliminary classifications of fixed-fee license agreements as either “Dynamic” or "Static," in 2017, approximately 70% of our fixed-fee revenue was derived from Dynamic Fixed-Fee Agreements, with the remainder coming from Static Fixed-Fee Agreements. Additionally, in the event a significant financing component is determined to exist in any of our agreements, we may recognize more or less revenue and corresponding interest expense or income, as appropriate. See below for a preliminary summary of expected adjustments related to our adoption of ASC 606. In addition, under our current accounting practices, we recognize revenue from our per-unit license agreements in the period in which we receive the related royalty report, generally one quarter in arrears from the period in which the underlying sales occur (i.e. on a "quarter-lag"). Upon adoption of the new guidance, we will be required to record per-unit royalty revenue in the same period in which the licensee’s underlying sales occur. Because we do not expect to receive the per-unit licensee royalty reports for sales during a given quarter within the time frame necessary to adequately review the reports and include the actual amounts in our quarterly results for such quarter, we expect to accrue the related revenue based on estimates of our licensees’ underlying sales, subject to certain constraints on our ability to estimate such amounts. As a result of accruing revenue for the quarter based on such estimates, adjustments will likely be required in the following quarter to true-up revenue to the actual amounts reported by our licensees. In addition, to the extent we receive prepayments related to per-unit license agreements that do not provide rights, over the term of the license, to future technologies that are highly interdependent or highly interrelated to the technologies provided at the inception of the agreement, we will recognize such prepayments as revenue in the period in which all remaining revenue recognition criteria have been met. We adopted the new guidance effective January 1, 2018, using the modified retrospective transition method. This will result in a cumulative effect adjustment to retained earnings. This adjustment is primarily the result of the recognition of deferred revenue balances related to our Static Agreements, the recognition of a significant financing component in certain of our Dynamic Fixed-Fee agreements, and related tax effects. The following table presents our preliminary estimate of the expected impact of these adjustments (in thousands). We will finalize and report the final adjustments in conjunction with the filing of our Quarterly Report on Form 10-Q for the quarter ended March 31, 2018. December 31, 2017 Static Fixed-Fee Agreements Static Prepayments Elimination of Quarter-Lag Reporting Significant Financing Component Related Tax Effects and Other Balance Sheet Impact Total Adjustments January 1, 2018 Accounts Receivable $ 216,293 $ 6,000 $ — $ 10,957 $ — $ (30,000 ) $ (13,043 ) $ 203,250 Deferred Tax Assets 84,582 — — — — (42,362 ) (42,362 ) 42,220 Taxes Payable 14,881 — — — — (1,184 ) (1,184 ) 13,697 Deferred Revenue (616,813 ) 99,466 85,146 — 3,235 30,000 217,847 (398,966 ) Retained Earnings (1,249,091 ) (105,466 ) (85,146 ) (10,957 ) (3,235 ) 43,546 (161,258 ) (1,410,349 ) We expect that as a result of our adoption of ASC 606, our January 1, 2018 deferred revenue balance will be $399.0 million, including $392.3 million related to Dynamic Fixed-Fee royalty payments. Under GAAP in effect as of December 31, 2017, approximately $525.0 million of our $616.8 million of deferred revenue balance as of December 31, 2017 related to Fixed-Fee arrangements. Our Fixed-Fee royalty payments are scheduled to amortize as follows (in thousands) under GAAP as of December 31, 2017 and under ASC 606, respectively: GAAP as of December 31, 2017 ASC 606 2018 $ 307,142 $ 184,272 2019 210,128 93,237 2020 2,618 69,047 2021 1,760 45,769 2022 1,245 — Thereafter 2,133 — $ 525,026 $ 392,325 Under ASC 606, the remaining $6.7 million of $399.0 million of deferred revenue is expected to be recorded when all revenue recognition criteria have been met. Accounting Standards Update: Leases In February 2016, the FASB issued ASU 2016-02, "Leases (Topic 842)," which outlines a comprehensive lease accounting model and supersedes the current lease guidance. The new guidance requires lessees to recognize lease liabilities and corresponding right-of-use assets for all leases with lease terms of greater than 12 months. It also changes the definition of a lease and expands the disclosure requirements of lease arrangements. The new guidance must be adopted using the modified retrospective approach and will be effective for the Company starting in first quarter 2020. Early adoption is permitted. We are in the process of determining the effect the adoption will have on our consolidated financial statements. Accounting Standards Update: Clarifying the Definition of a Business In January 2017, the FASB issued ASU 2017-01, “Business Combinations (Topic 805): Clarifying the Definition of a Business." ASU 2017-01 narrows the existing definition of a business and provides a framework for evaluating whether a transaction should be accounted for as an acquisition (or disposal) of assets or a business. The guidance requires an entity to evaluate whether substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or a group of similar identifiable assets; if so, the set of transferred assets and activities (collectively, the "set") is not a business. To be considered a business, the set would need to include an input and a substantive process that together significantly contribute to the ability to create outputs, as defined by the ASU. We adopted this guidance early, in first quarter 2017, and it had no immediate impact on our consolidated financial statements. Accounting Standards Update: Simplifying the Test for Goodwill Impairment In January 2017, the FASB issued ASU No. 2017-04, "Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment," which eliminates the requirement to calculate the implied fair value of goodwill to measure a goodwill impairment charge (Step 2) from the goodwill impairment test. Instead, an impairment charge will equal the amount by which a reporting unit’s carrying amount exceeds its fair value, not to exceed the amount of goodwill allocated to the reporting unit. We adopted this guidance early, in first quarter 2017, and it had no immediate impact on our consolidated financial statements. Accounting Standards Update: Statement of Cash Flows In August 2016, the FASB issued ASU No. 2016-15, "Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments," which eliminates the diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. We adopted this guidance early, in second quarter 2017, and it had no immediate impact on our consolidated financial statements. Accounting Standards Update: Financial Instruments In January 2016, the FASB issued ASU No. 2016-01, "Financial Instruments (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities," which amends certain measurement, presentation, and disclosure requirements for financial instruments. The new guidance must be adopted by means of a cumulative-effect adjustment to the balance sheet in the year of adoption and will be effective for the Company starting in first quarter 2018. Early adoption is permitted. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements. Accounting Standards Update: Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income In February 2018, the FASB issued ASU No. 2018-02, "Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income," which allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Reform Act. The guidance is effective for fiscal years beginning after December 15, 2018 and early adoption is permitted. We expect to early adopt this guidance in first quarter 2018 and it is not expected to have a material effect on our consolidated financial statements.

Summary of Significant Accoun21

Summary of Significant Accounting Policies Foreign Currency Translation (Policies)	12 Months Ended
	Dec. 31, 2017
Foreign Currency Translation [Abstract]
Foreign Currency Transactions and Translations Policy [Policy Text Block]	Foreign Currency Translation The functional currency of substantially all of the Company's wholly-owned subsidiaries is the U.S. dollar. Certain subsidiaries have monetary assets and liabilities that are denominated in a currency that is different than the functional currency. The gains and losses resulting from this remeasurement and translation of monetary assets denominated in a currency that is different than the functional currency are reflected in the determination of net income (loss).

Summary of Significant Accoun22

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements [Abstract]
Schedule of Cash and Cash Equivalents [Table Text Block]	Cash and cash equivalents at December 31, 2017 and 2016 consisted of the following (in thousands): December 31, 2017 2016 Money market and demand accounts $ 417,348 $ 404,074 Commercial paper 15,666 — $ 433,014 $ 404,074
Realized Gain (Loss) on Investments [Table Text Block]	The gross realized gains and losses on sales of marketable securities were not significant during the years ended December 31, 2017, 2016 and 2015.
Available-for-sale Securities [Table Text Block]	Marketable securities as of December 31, 2017 and 2016 consisted of the following (in thousands): December 31, 2017 Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Available-for-sale securities Commercial paper 66,132 — — 66,132 U.S. government securities 513,645 — (2,613 ) 511,032 Corporate bonds, asset backed and other securities 164,075 35 (627 ) 163,483 Total available-for-sale securities $ 743,852 $ 35 $ (3,240 ) $ 740,647 Reported in: Cash and cash equivalents $ 15,666 Short-term investments 724,981 Total marketable securities $ 740,647
Fair Value, Measurement Inputs, Disclosure [Table Text Block]	Fair Value Measurements We use various valuation techniques and assumptions when measuring the fair value of our assets and liabilities. We utilize market data or assumptions that market participants would use in pricing the asset or liability, including assumptions about risk and the risks inherent in the inputs to the valuation technique. This guidance established a hierarchy that prioritizes fair value measurements based on the types of input used for the various valuation techniques (market approach, income approach and cost approach). The levels of the hierarchy are described below: Level 1 Inputs — Level 1 includes financial instruments for which quoted market prices for identical instruments are available in active markets. Level 2 Inputs — Level 2 includes financial instruments for which there are inputs other than quoted prices included within Level 1 that are observable for the instrument such as quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets with insufficient volume or infrequent transactions (less active markets) or model-driven valuations in which significant inputs are observable or can be derived principally from, or corroborated by, observable market data, including market interest rate curves, referenced credit spreads and pre-payment rates. Level 3 Inputs — Level 3 includes financial instruments for which fair value is derived from valuation techniques including pricing models and discounted cash flow models in which one or more significant inputs are unobservable, including the company’s own assumptions. The pricing models incorporate transaction details such as contractual terms, maturity and, in certain instances, timing and amount of future cash flows, as well as assumptions related to liquidity and credit valuation adjustments of marketplace participants. Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of financial assets and financial liabilities and their placement within the fair value hierarchy. We use quoted market prices for similar assets to estimate the fair value of our Level 2 investments. Our financial assets are included within short-term investments on our consolidated balance sheets, unless otherwise indicated. Our financial assets that are accounted for at fair value on a recurring basis are presented in the tables below as of December 31, 2017 and December 31, 2016 (in thousands): Fair Value as of December 31, 2017 Level 1 Level 2 Level 3 Total Assets: Money market and demand accounts (a) $ 417,348 $ — $ — $ 417,348 Commercial paper (b) — 66,132 — 66,132 U.S. government securities — 511,032 — 511,032 Corporate bonds, asset backed and other securities — 163,483 — 163,483 $ 417,348 $ 740,647 $ — $ 1,157,995 _______________ (a) Included within cash and cash equivalents. (b) Includes $15.7 million of commercial paper that is included within cash and cash equivalents. Fair Value as of December 31, 2016 Level 1 Level 2 Level 3 Total Assets: Money market and demand accounts (a) $ 404,074 $ — $ — $ 404,074 Commercial paper — 113,490 — 113,490 U.S. government securities — 224,330 — 224,330 Corporate bonds and asset backed securities — 210,867 — 210,867 $ 404,074 $ 548,687 $ — $ 952,761 _______________ (a) Included within cash and cash equivalents.
Schedule of Finite-Lived Intangible Assets by Major Class [Table Text Block]	patents consisted of the following (in thousands, except for useful life data): December 31, 2017 2016 Weighted average estimated useful life (years) 10.0 9.9 Gross patents $ 660,886 $ 593,309 Accumulated amortization (335,478 ) (282,541 ) Patents, net $ 325,408 $ 310,768
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]	The estimated aggregate amortization expense for the next five years related to our patents balance as of December 31, 2017 is as follows (in thousands): 2018 $ 53,547 2019 50,672 2020 45,871 2021 41,272 2022 38,654
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Table Text Block]	Deferred charges are recorded in our Consolidated Balance Sheets within the following captions (in thousands): December 31, 2017 2016 Prepaid and other current assets Deferred commission expense $ 59 $ 187 Other non-current assets Deferred commission expense 48 181 Long-term debt (including current portion of long-term debt) Deferred financing costs 3,011 4,401
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	The following table reconciles the numerator and the denominator of the basic and diluted net income per share computation (in thousands, except for per share data): For the Year Ended December 31, 2017 2016 2015 Basic Diluted Basic Diluted Basic Diluted Numerator: Net income applicable to common shareholders $ 174,293 $ 174,293 $ 309,001 $ 309,001 $ 119,225 $ 119,225 Denominator: Weighted-average shares outstanding: Basic 34,605 34,605 34,526 34,526 36,048 36,048 Dilutive effect of stock options, RSUs and convertible securities 1,174 663 415 Weighted-average shares outstanding: Diluted 35,779 35,189 36,463 Earnings Per Share: Net income: Basic $ 5.04 5.04 $ 8.95 8.95 $ 3.31 3.31 Dilutive effect of stock options, RSUs and convertible securities (0.17 ) (0.17 ) (0.04 ) Net income: Diluted $ 4.87 $ 8.78 $ 3.27

Geographic Concentration (Table

Geographic Concentration (Tables)	12 Months Ended
	Dec. 31, 2017
GEOGRAPHIC CUSTOMER CONCENTRATION [Abstract]
Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block]	The table below lists the countries of the headquarters of our licensees and customers and the total revenue derived from each country or region for the periods indicated (in thousands): For the Year Ended December 31, 2017 2016 2015 United States $ 194,184 $ 199,928 $ 65,703 South Korea 113,059 69,000 69,000 China 77,087 154,767 2,768 Canada 74,107 10,719 13,151 Taiwan 36,051 185,645 218,584 Japan 25,210 27,685 53,775 Sweden 6,935 6,934 6,934 Other Europe 4,413 4,713 4,807 Germany 1,892 6,463 6,712 Other Asia — — 1 Total $ 532,938 $ 665,854 $ 441,435 During 2017 , 2016 and 2015 , the following licensees or customers accounted for 10% or more of total revenues: 2017 2016 2015 Apple (a) 21 % 25 % — % Huawei (b) 14 % 23 % — % Samsung 13 % 10 % 16 % Blackberry (c) 13 % < 10% < 10% Pegatron < 10% 20 % 31 % Sony (d) < 10% < 10% 14 % (a) 2016 revenues include $141.4 million of past patent royalties. (b) 2017 and 2016 revenues include $8.4 million and $121.5 million , respectively, of past patent royalties. (c) 2017 revenues include $70.7 million of past patent royalties. (d) 2015 revenues include $21.9 million of past patent royalties. At December 31, 2017, 2016 and 2015, we held $336.1 million , $287.2 million and $289.7 million , respectively, of our property and equipment and patents in the United States net of accumulated depreciation and amortization, or nearly 100% of our property and equipment and 100% of our patents. At each of December 31, 2017, 2016 and 2015, we held less than $0.3 million of property and equipment, net of accumulated depreciation, collectively, in Canada, Europe and Asia.
Schedule of Revenue by Major Customers by Reporting Segments [Table Text Block]	ing 2017 , 2016 and 2015 , the following licensees or customers accounted for 10% or more of total revenues: 2017 2016 2015 Apple (a) 21 % 25 % — % Huawei (b) 14 % 23 % — % Samsung 13 % 10 % 16 % Blackberry (c) 13 % < 10% < 10% Pegatron < 10% 20 % 31 % Sony (d) < 10% < 10% 14 % (a) 2016 revenues include $141.4 million of past patent royalties. (b) 2017 and 2016 revenues include $8.4 million and $121.5 million , respectively, of past patent royalties. (c) 2017 revenues include $70.7 million of past patent royalties. (d) 2015 revenues include $21.9 million of past patent royalties. At December 31, 2017, 2016 and 2015, we held $336.1 million , $287.2 million and $289.7 million , respectively, of our property and equipment and patents in the United States net of accumulated depreciation and amortization, or nearly 100% of our property and equipment and 100% of our patents. At each of December 31, 2017, 2016 and 2015, we held less than $0.3 million of property and equipment, net of accumulated depreciation, collectively, in Canada, Europe and Asia.

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property and Equipment [Abstract]
Property, Plant and Equipment [Table Text Block]	December 31, 2017 2016 Computer equipment and software $ 20,003 $ 18,480 Engineering and test equipment 4,034 3,767 Building and improvements 3,624 3,576 Leasehold improvements 9,711 9,692 Furniture and fixtures 1,279 1,247 Property and equipment, gross 38,651 36,762 Less: accumulated depreciation (27,978 ) (24,136 ) Property and equipment, net $ 10,673 $ 12,626

Obligations (Tables)

Obligations (Tables)	12 Months Ended
	Dec. 31, 2017
OBLIGATIONS: [Abstract]
Schedule of Debt [Table Text Block]	December 31, 2017 2016 1.50% Senior Convertible Notes due 2020 $ 316,000 $ 316,000 Less: Unamortized interest discount (27,863 ) (39,578 ) Deferred financing costs (3,011 ) (4,401 ) Total debt obligations 285,126 272,021 Less: Current portion of long-term debt — — Long-term debt obligations $ 285,126 $ 272,021
Schedule of Maturities of Long-term Debt [Table Text Block]	Maturities of principal of the long-term debt obligations of the Company as of December 31, 2017 are as follows (in thousands): 2018 $ — 2019 — 2020 316,000 2021 — 2022 — Thereafter — $ 316,000
Schedule of Long-term Debt Instruments [Table Text Block]	The following table presents the amount of interest cost recognized for the years ended December 31, 2017 , 2016 and 2015 related to the contractual interest coupon, accretion of the debt discount and the amortization of financing costs (in thousands). For the Year Ended December 31, 2017 2016 2015 Contractual coupon interest $ 4,740 $ 6,178 $ 9,568 Accretion of debt discount 11,715 13,536 18,384 Amortization of financing costs 1,390 1,716 2,485 Total $ 17,845 $ 21,430 $ 30,437

Commitments (Tables)

Commitments (Tables)	12 Months Ended
	Dec. 31, 2017
COMMITMENTS [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	Minimum future payments for operating leases and purchase commitments as of December 31, 2017 are as follows (in thousands): 2018 $ 4,784 2019 4,499 2020 2,918 2021 2,377 2022 2,131 Thereafter 4,741

Compensation Plans and Progra27

Compensation Plans and Programs (Tables)	12 Months Ended
	Dec. 31, 2017
COMPENSATION PLANS AND PROGRAMS [Abstract]
Schedule of RSU Award Vesting	9. COMPENSATION PLANS AND PROGRAMS Compensation Programs We use a variety of compensation programs to both attract and retain employees, and to more closely align employee compensation with company performance. These programs include, but are not limited to, short-term incentive awards tied to performance goals and cash awards to inventors for filed patent applications and patent issuances, as well as stock option awards, time-based RSU awards and performance-based RSU awards under the LTCP. Our LTCP typically includes annual time-based RSU grants with a three-year vesting period, as well as annual performance-based RSU awards with a three to five-year performance period; as a result, in any one year, we are typically accounting for at least three active LTCP cycles. We issue new shares of our common stock to satisfy our obligations under the share-based components of these programs. However, our Board of Directors has the right to authorize the issuance of treasury shares to satisfy such obligations in the future. Equity Incentive Plans On June 14, 2017, our shareholders adopted and approved the 2017 Equity Incentive Plan (the "2017 Plan"), under which employees, directors and consultants can receive share-based awards such as RSUs, restricted stock and stock options as well as other stock or cash awards. From June 2009 through June 14, 2017, we granted such awards pursuant to our 2009 Stock Incentive Plan (the “2009 Plan," and, together with the 2017 Plan, the "Equity Plans"), which was adopted and approved by our shareholders on June 4, 2009, and the material terms of which were re-approved on June 12, 2014. Upon the adoption of the 2017 Plan in June 2017, the 2009 Plan was terminated and all shares remaining available for grant under the 2009 Plan were canceled. The number of shares available for issuance under the 2017 Plan is equal to 2,400,000 shares plus any shares subject to awards granted under the 2009 Plan that, on or after June 14, 2017, expire or otherwise terminate without having been exercised in full, or that are forfeited to or repurchased by us. The following table summarizes changes in the number of equity instruments available for grant (in thousands) under the Equity Plans for the current year: Available for Grant Balance at December 31, 2016 1,236 RSUs granted (a) (295 ) Options granted (25 ) Options expired and RSUs canceled 246 Balance at June 14, 2017 1,162 Remaining available shares canceled under 2009 Plan (1,162 ) Shares authorized under 2017 Plan 2,400 RSUs granted (a) (8 ) Options expired and RSUs canceled 11 Balance at December 31, 2017 2,403 (a) RSUs granted include time-based RSUs, performance-based RSUs and dividend equivalents credited. RSUs and Restricted Stock We may issue RSUs and/or shares of restricted stock to officers, employees, non-employee directors and consultants. Any cancellations of outstanding RSUs granted under the Equity Plans will increase the number of RSUs and/or shares of restricted stock remaining available for grant under the 2017 Plan. Time-based RSUs vest over periods generally ranging from 1 to 3 years from the date of the grant. Performance-based RSUs generally have a vesting period of between 3 and 5 years. During 2017 and 2016, we granted approximately 0.2 million and 0.4 million RSUs, respectively, under the Equity Plans. At December 31, 2017 and 2016, we had unrecognized compensation cost related to share-based awards of $13.6 million and $24.8 million , respectively. For grants made in 2017, 2016 and 2015 that cliff vest, we expect to amortize the associated unrecognized compensation cost at December 31, 2017 on a straight-line basis over a three-year period. Vesting of performance-based RSU awards is subject to attainment of specific goals established by the Compensation Committee of the Board of Directors. Depending upon performance against these goals, the payout range for performance-based RSU awards can be anywhere from 0 to 2 times the value of the award. Information with respect to current RSU activity is summarized as follows (in thousands, except per share amounts): Number of Unvested RSUs Weighted Average Per Share Grant Date Fair Value Balance at December 31, 2016 1,398 $ 46.65 Granted* 317 58.63 Forfeited* (22 ) 63.30 Vested* (688 ) 35.14 Balance at December 31, 2017 1,005 $ 57.95 * These numbers include less than 0.1 million RSUs credited on unvested RSU awards as dividend equivalents. Dividend equivalents accrue with respect to unvested RSU awards when and as cash dividends are paid on the Company's common stock, and vest if and when the underlying RSUs vest. Granted amounts include performance-based RSU awards at their maximum potential payout level of 200%. The total vest date fair value of the RSUs that vested in 2017, 2016 and 2015 was $56.0 million , $9.8 million and $26.3 million , respectively. The weighted average per share grant date fair value of the awards that vested in 2017, 2016 and 2015 was $35.14 , $44.08 and $41.29 , respectively. Other RSU Grants We also grant RSUs to all non-management Board members, certain consultants and, in special circumstances, management personnel outside of the LTCP. Grants of this type are supplemental to any awards granted to management personnel through the LTCP. Stock Options The 2009 Plan allowed, and the 2017 Plan allows, for the granting of incentive and non-qualified stock options, as well as other securities. The administrator of the Equity Plans, the Compensation Committee of the Board of Directors, determines the number of options to be granted, subject to certain limitations set forth in the 2017 Plan. Annually, since 2013, both incentive and non-qualified stock options have been granted pursuant to the LTCP. Under the terms of the Equity Plans, the exercise price per share of each option, other than in the event of options granted in connection with a merger or other acquisition, cannot be less than 100% of the fair market value of a share of common stock on the date of grant. Options granted under the Equity Plans are generally exercisable for a period of between 7 to 10 years from the date of grant and may vest on the grant date, another specified date or over a period of time. We also have approximately 0.1 million options outstanding under a prior stock plan that have an indefinite contractual life. Information with respect to current year stock option activity is summarized as follows (in thousands, except per share amounts): Outstanding Options Weighted Balance at December 31, 2016 515 $ 37.38 Granted 25 85.85 Canceled — — Exercised (9 ) 44.20 Balance at December 31, 2017 531 $ 39.55 The weighted average remaining contractual life of our outstanding options was 8.50 years as of December 31, 2017 . We currently have approximately 0.1 million options outstanding that have an indefinite contractual life. These options were granted between 1983 and 1986 under a prior stock plan. For purposes of calculating the weighted average remaining contractual life, these options were assigned an original life in excess of 50 years. The majority of these options have an exercise price between $9.00 and $11.63 . The total intrinsic value of stock options exercised during the years ended December 31, 2017 , 2016 and 2015 was $0.3 million , $1.5 million and $0.2 million , respectively. The total intrinsic value of our options outstanding at December 31, 2017 was $19.7 million . In 2017 , we recorded cash received from the exercise of options of approximately $0.4 million . Upon option exercise, we issued new shares of stock. At both December 31, 2017 and 2016 , we had approximately 0.5 million options outstanding that had exercise prices less than the fair market value of our stock at the respective balance sheet date. These options would have generated cash proceeds to the Company of $21.2 million and $19.4 million , respectively, if they had been fully exercised on those dates. Defined Contribution Plans We have a 401(k) plan (“Savings Plan”) wherein employees can elect to defer compensation within federal limits. We match a portion of employee contributions. Our 401(k) contribution expense was approximately $1.4 million , $1.1 million and $1.2 million for 2017 , 2016 and 2015 , respectively. At our discretion, we may also make a profit-sharing contribution to our employees’ 401(k) accounts. Additionally, the company contributed $0.3 million , $0.5 million and $0.2 million in 2017, 2016 and 2015, respectively, to other defined contribution plans.
Schedule of Equity Instruments Available for Grant [Table Text Block]	The following table summarizes changes in the number of equity instruments available for grant (in thousands) under the Equity Plans for the current year: Available for Grant Balance at December 31, 2016 1,236 RSUs granted (a) (295 ) Options granted (25 ) Options expired and RSUs canceled 246 Balance at June 14, 2017 1,162 Remaining available shares canceled under 2009 Plan (1,162 ) Shares authorized under 2017 Plan 2,400 RSUs granted (a) (8 ) Options expired and RSUs canceled 11 Balance at December 31, 2017 2,403 (a) RSUs granted include time-based RSUs, performance-based RSUs and dividend equivalents credited.
Share-based Compensation, Stock Options, Activity [Table Text Block]	Information with respect to current year stock option activity is summarized as follows (in thousands, except per share amounts): Outstanding Options Weighted Balance at December 31, 2016 515 $ 37.38 Granted 25 85.85 Canceled — — Exercised (9 ) 44.20 Balance at December 31, 2017 531 $ 39.55

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
TAXES [Abstract]
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	Our income tax provision consists of the following components for 2017 , 2016 and 2015 (in thousands): 2017 2016 2015 Current Federal $ 3,656 $ 14,637 $ 42,181 State (1 ) (60 ) 415 Foreign source withholding tax 47,592 79,932 55,276 51,247 94,509 97,872 Deferred Federal 21,671 (48,086 ) (89,026 ) State (1,074 ) (557 ) 554 Foreign source withholding tax 49,832 70,925 55,221 70,429 22,282 (33,251 ) Total $ 121,676 $ 116,791 $ 64,621 The d
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]	The deferred tax assets and liabilities were comprised of the following components at December 31, 2017 and 2016 (in thousands): 2017 Federal State Foreign Total Net operating losses $ 1,804 $ 122,364 $ 988 $ 125,156 Deferred revenue, net 9,058 35 29,189 38,282 Stock compensation 6,643 2,293 — 8,936 Patent amortization 16,052 7 — 16,059 Depreciation (214 ) (65 ) — (279 ) Other-than-temporary impairment 379 71 — 450 Other accrued liabilities 268 (26 ) — 242 Other employee benefits 3,449 649 — 4,098 37,439 125,328 30,177 192,944 Less: valuation allowance (1,773 ) (121,155 ) (988 ) (123,916 ) Net deferred tax asset $ 35,666 $ 4,173 $ 29,189 $ 69,028	2016 Federal State Foreign Total Net operating losses $ — $ 89,162 $ 463 $ 89,625 Deferred revenue, net 60,320 288 31,686 92,294 Stock compensation 12,648 2,038 — 14,686 Patent amortization 24,145 — — 24,145 Depreciation (502 ) (70 ) — (572 ) Other accrued liabilities 4,483 321 — 4,804 Other-than-temporary impairment 558 61 — 619 Other employee benefits 2,524 275 — 2,799 104,176 92,075 32,149 228,400 Less: valuation allowance — (89,352 ) (463 ) (89,815 ) Net deferred tax asset $ 104,176 $ 2,723 $ 31,686 $ 138,585
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	The following is a reconciliation of income taxes at the federal statutory rate with income taxes recorded by the Company for the years ended December 31, 2017 , 2016 and 2015 (in thousands): 2017 2016 2015 Tax at U.S. statutory rate 35.0 % 35.0 % 35.0 % State tax provision — % (0.1 )% 0.5 % Change in federal and state valuation allowance 0.5 % 0.1 % — % Research and development tax credits (0.8 )% (0.5 )% (1.2 )% Uncertain tax positions (2.4 )% 2.1 % — % Permanent differences 1.0 % 0.6 % 1.2 % Domestic production activities deduction (2.0 )% (9.8 )% — % Stock compensation (4.0 )% — % — % Rate change (a) 14.6 % — % — % Other (0.3 )% 0.3 % 0.2 % Total tax provision (b) 41.6 % 27.7 % 35.7 %
Summary of Positions for which Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Table Text Block]	The following is a roll forward of our total gross unrecognized tax benefits, which if reversed would impact the effective tax rate, for the fiscal years 2015 through 2017 (in thousands): 2017 2016 2015 Balance as of January 1 $ 10,397 $ 1,469 $ 1,361 Tax positions related to current year: Additions 1,009 3,209 141 Reductions — — — Tax positions related to prior years: Additions — 6,281 — Reductions (1,610 ) — (33 ) Settlements (6,544 ) (562 ) — Lapses in statues of limitations — — — Balance as of December 31 $ 3,252 $ 10,397 $ 1,469

Equity Transactions (Tables)

Equity Transactions (Tables)	12 Months Ended
	Dec. 31, 2017
EQUITY TRANSACTIONS: [Abstract]
Dividends Declared [Table Text Block]	2017 Per Share Total Cumulative by Fiscal Year First quarter $ 0.30 $ 10,404 $ 10,404 Second quarter 0.30 10,413 20,817 Third quarter 0.35 12,149 32,966 Fourth quarter 0.35 12,156 45,122 $ 1.30 $ 45,122 2016 First quarter $ 0.20 $ 6,923 $ 6,923 Second quarter 0.20 6,861 13,784 Third quarter 0.30 10,285 24,069 Fourth quarter 0.30 10,290 34,359 $ 1.00 $ 34,359

Selected Quarterly Results (Tab

Selected Quarterly Results (Tables)	12 Months Ended
	Dec. 31, 2016
SELECTED QUARTERLY RESULTS (Unaudited) [Abstract]
Schedule of Quarterly Financial Information [Table Text Block]	The table below presents quarterly data for the years ended December 31, 2017 and 2016 : First Second Third Fourth (In thousands, except per share amounts, unaudited) 2017 Revenues (a) $ 94,530 $ 135,779 $ 97,325 $ 205,304 Net income applicable to InterDigital, Inc.'s common shareholders $ 33,756 $ 52,499 $ 35,536 $ 52,502 Net income per common share — basic $ 0.98 $ 1.51 $ 1.02 $ 1.52 Net income per common share — diluted $ 0.93 $ 1.46 $ 1.00 $ 1.48 2016 Revenues (b) $ 107,764 $ 75,915 $ 208,307 $ 273,868 Net income applicable to InterDigital, Inc.'s common shareholders $ 28,071 $ 39,994 $ 104,466 $ 136,470 Net income per common share — basic $ 0.80 $ 1.16 $ 3.05 $ 3.98 Net income per common share — diluted $ 0.79 $ 1.14 $ 2.99 $ 3.85

Balance Sheet Parenthetical (De

Balance Sheet Parenthetical (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Balance Sheet Parenthetical [Abstract]
Allowance for doubtful accounts	$ 456	$ 0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	70,749,000	70,318,000
Common stock, shares outstanding	34,622,000	34,298,000
Preferred stock, par value	$ 0.10	$ 0.10
Preferred stock, shares authorized	14,399,000	14,399,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Treasury stock, 36,020 and 34,716 shares of common held at cost	36,127,000	36,020,000

Summary of Significant Accoun32

Summary of Significant Accounting Policies Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	$ 743,852	$ 549,479
Other than Temporary Impairment Losses, Investments		200
Short-term Investments	724,981	548,687
Assets, Fair Value Disclosure, Recurring	1,157,995	952,761
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	345,000	404,800
Cash and Cash Equivalents, at Carrying Value	433,014	404,074	$ 510,207	$ 428,567
Other Comprehensive Income (Loss), Net of Tax	(1,569)	(336)	$ (296)
Available-for-sale Securities, Gross Unrealized Gain	35	37
Available-for-sale Securities, Gross Unrealized Loss	(3,240)	(829)
Fair Value, Inputs, Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	740,647	548,687
Assets, Fair Value Disclosure, Recurring	740,647	548,687
Fair Value, Inputs, Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets, Fair Value Disclosure, Recurring	417,348	404,074
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	66,132	113,490
Cash and Cash Equivalents, at Carrying Value	15,666	0
Available-for-sale Securities, Gross Unrealized Gain	0	0
Available-for-sale Securities, Gross Unrealized Loss	0	0
Commercial Paper [Member] | Fair Value, Inputs, Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	66,132	113,490
Money Market Funds and Demand Deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, at Carrying Value	417,348	404,074
US Government Corporations and Agencies Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	513,645	224,583
Available-for-sale Securities, Gross Unrealized Gain	0	9
Available-for-sale Securities, Gross Unrealized Loss	(2,613)	(262)
US Government Corporations and Agencies Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	511,032	224,330
Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	164,075	211,406
Available-for-sale Securities, Gross Unrealized Gain	35	28
Available-for-sale Securities, Gross Unrealized Loss	(627)	(567)
Corporate Bond Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	$ 163,483	$ 210,867

Summary of Significant Accoun33

Summary of Significant Accounting Policies Short-Term Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Short-term Investments	$ 724,981	$ 548,687
Available-for-sale Securities	743,852	549,479
Available-for-sale Securities, Gross Unrealized Gain	35	37
Available-for-sale Securities, Gross Unrealized Loss	(3,240)	(829)
Other than Temporary Impairment Losses, Investments		200
Other Comprehensive Income (Loss), Net of Tax	(1,569)	(336)	$ (296)
Assets, Fair Value Disclosure, Recurring	1,157,995	952,761
Available-for-sale Securities, Debt Maturities, within One Year, Fair Value	345,000	404,800
US Government Corporations and Agencies Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	513,645	224,583
Available-for-sale Securities, Gross Unrealized Gain	0	9
Available-for-sale Securities, Gross Unrealized Loss	(2,613)	(262)
Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	164,075	211,406
Available-for-sale Securities, Gross Unrealized Gain	35	28
Available-for-sale Securities, Gross Unrealized Loss	(627)	(567)
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	66,132	113,490
Available-for-sale Securities, Gross Unrealized Gain	0	0
Available-for-sale Securities, Gross Unrealized Loss	0	0
Fair Value, Inputs, Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	740,647	548,687
Assets, Fair Value Disclosure, Recurring	740,647	548,687
Fair Value, Inputs, Level 2 [Member] | US Government Corporations and Agencies Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	511,032	224,330
Fair Value, Inputs, Level 2 [Member] | Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	163,483	210,867
Fair Value, Inputs, Level 2 [Member] | Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	$ 66,132	$ 113,490

Summary of Significant Accoun34

Summary of Significant Accounting Policies Fair Value Measurements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Apr. 04, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 433,014	$ 404,074	$ 510,207	$ 428,567
Senior Notes	$ 285,126	$ 272,021			$ 230,000
Concentration Risk, Additional Characteristic	three	four
Concentration Risk, Percentage	96.00%	91.00%
Assets, Fair Value Disclosure, Recurring	$ 1,157,995	$ 952,761
Long-term Debt, Excluding Current Maturities	285,126	272,021
Long-term Debt, Fair Value	377,029	428,575
Money Market Funds and Demand Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	417,348	404,074
Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	66,132	113,490
US Treasury and Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	511,032	224,330
Corporate Bonds and Asset Backed Securities [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	163,483
Corporate Bond Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring		210,867
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	417,348	404,074
Fair Value, Inputs, Level 1 [Member] | Money Market Funds and Demand Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	417,348	404,074
Fair Value, Inputs, Level 1 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Fair Value, Inputs, Level 1 [Member] | US Treasury and Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Fair Value, Inputs, Level 1 [Member] | Corporate Bonds and Asset Backed Securities [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0
Fair Value, Inputs, Level 1 [Member] | Corporate Bond Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring		0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	740,647	548,687
Fair Value, Inputs, Level 2 [Member] | Money Market Funds and Demand Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Fair Value, Inputs, Level 2 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	66,132	113,490
Fair Value, Inputs, Level 2 [Member] | US Treasury and Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	511,032	224,330
Fair Value, Inputs, Level 2 [Member] | Corporate Bonds and Asset Backed Securities [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	163,483
Fair Value, Inputs, Level 2 [Member] | Corporate Bond Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring		210,867
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Fair Value, Inputs, Level 3 [Member] | Money Market Funds and Demand Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Fair Value, Inputs, Level 3 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Fair Value, Inputs, Level 3 [Member] | US Treasury and Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Fair Value, Inputs, Level 3 [Member] | Corporate Bonds and Asset Backed Securities [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0
Fair Value, Inputs, Level 3 [Member] | Corporate Bond Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring		0
Convertible Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes	$ 316,000	$ 316,000

Summary of Significant Accoun35

Summary of Significant Accounting Policies Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2017
Building [Member]
Property, Plant and Equipment [Line Items]
Useful Life, Minimum	25 years
Minimum [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Useful Life, Minimum	3 years
Minimum [Member] | Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Useful Life, Minimum	5 years
Maximum [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Useful Life, Minimum	5 years
Maximum [Member] | Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Useful Life, Minimum	10 years

Summary of Significant Accoun36

Summary of Significant Accounting Policies Internal-Use Software Costs (Details)	12 Months Ended
	Dec. 31, 2017
Software Development [Member]
Property, Plant and Equipment [Line Items]
Useful Life, Minimum	2 years

Summary of Significant Accoun37

Summary of Significant Accounting Policies Investment in Other Entities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Cost and Equity method Investments [Line Items]
Payments for (Proceeds from) Long-term Investments	$ 4,585	$ 2,000	$ 12,623
Long-term Investments	$ 19,200	$ 14,600

Summary of Significant Accoun38

Summary of Significant Accounting Policies Patents (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	$ 237
Finite-Lived Intangible Assets, Net	325,408	$ 310,768
Finite-Lived Intangible Assets, Amortization Expense, Year Two	237
Finite-Lived Intangible Assets, Amortization Expense, Year Three	237
Finite-Lived Intangible Assets, Amortization Expense, Year Four	237
Finite-Lived Intangible Assets, Amortization Expense, Year Five	$ 237
Developed Technology Rights [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	10 years
Patents Purchased [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	9 years 10 months
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	10 years	9 years 11 months
Finite-Lived Patents, Gross	$ 660,886	$ 593,309
Finite-Lived Intangible Assets, Accumulated Amortization	(335,478)	(282,541)
Finite-Lived Intangible Assets, Net	53,547
Finite-Lived Intangible Assets, Amortization Expense, Year Two	50,672
Finite-Lived Intangible Assets, Amortization Expense, Year Three	45,871
Finite-Lived Intangible Assets, Amortization Expense, Year Four	41,272
Finite-Lived Intangible Assets, Amortization Expense, Year Five	38,654
Finite-Lived Intangible Assets, Amortization Expense	$ 52,900	$ 48,600	$ 44,000

Summary of Significant Accoun39

Summary of Significant Accounting Policies Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	$ 237
Finite-Lived Intangible Assets, Net	325,408	$ 310,768
Finite-Lived Intangible Assets, Amortization Expense, Year Two	237
Finite-Lived Intangible Assets, Amortization Expense, Year Three	237
Finite-Lived Intangible Assets, Amortization Expense, Year Four	237
Finite-Lived Intangible Assets, Amortization Expense, Year Five	237
Finite-Lived Intangible Assets, Amortization Expense, after Year Five	$ 878
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	9 years
Finite-Lived Trade Names, Gross	$ 600	600
Finite-Lived Intangible Assets, Accumulated Amortization	$ (67)	0
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	10 years
Finite-Lived Intangible Assets, Accumulated Amortization	$ (170)	0
Finite-Lived Customer Relationships, Gross	$ 1,700	$ 1,700

Summary of Significant Accoun40

Summary of Significant Accounting Policies Deferred Charges (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2011
Deferred Charges [Line Items]
Payments for Commissions		$ 300
Contract Revenue Cost			$ 100	$ 100
Payments of Debt Issuance Costs		0	0	9,403
Sales Commissions and Fees		200	400	600
Amortization of Financing Costs		1,390	1,716	$ 2,485
Deferred Finance Costs, Gross		3,011	4,401
Deferred Sales Commission Current [Member]
Deferred Charges [Line Items]
Other Deferred Costs, Net		59	187
Deferred Sales Commission Non-Current [Member]
Deferred Charges [Line Items]
Other Deferred Costs, Net		$ 48	$ 181
Convertible Debt [Member]
Deferred Charges [Line Items]
Payments of Debt Issuance Costs	$ 9,300
Convertible Debt [Member] | Other Long-term Liabilities [Member]
Deferred Charges [Line Items]
Payments of Debt Issuance Costs	$ 7,000
Convertible Debt [Member] | Equity [Member]
Deferred Charges [Line Items]
Payments of Debt Issuance Costs					$ 1,500

Summary of Significant Accoun41

Summary of Significant Accounting Policies Research and Development (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Research and Development [Abstract]
Development Expense	$ 70,708	$ 68,733	$ 72,702

Summary of Significant Accoun42

Summary of Significant Accounting Policies Impairment of Long-Lived Assets (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Long-Lived Assets to be Disposed of	$ 0.2

Summary of Significant Accoun43

Summary of Significant Accounting Policies Income Tax (Details) - USD ($) $ in Thousands	12 Months Ended			144 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Income Tax Contingency [Line Items]
Income taxes paid, including foreign witholding taxes	$ 66,793	$ 108,635	$ 85,780
Income Tax Expense (Benefit)	121,676	116,791	64,621
Unrecognized Tax Benefits, Increases Resulting from Prior Period Tax Positions	0	6,281	0
Foreign Tax Authority [Member]
Income Tax Contingency [Line Items]
Income taxes paid, including foreign witholding taxes	46,700	79,900	55,300	$ 422,300
Research and Development Arrangement [Member]
Income Tax Contingency [Line Items]
Income Tax Expense (Benefit)	2,300	2,100	$ 2,100
Research and Development Arrangement [Member] | Tax Year 2016 [Member]
Income Tax Contingency [Line Items]
Income Tax Expense (Benefit)	23,600
Federal
Income Tax Contingency [Line Items]
Income Tax Expense (Benefit)	5,100	$ 8,300
2017 Income Tax Reform [Domain]
Income Tax Contingency [Line Items]
Income Tax Expense (Benefit)	$ 42,600
ForeignGovenmentswithUSTaxTreaties [Domain] | Foreign Tax Authority [Member]
Income Tax Contingency [Line Items]
Income taxes paid, including foreign witholding taxes				$ 275,200

Summary of Significant Accoun44

Summary of Significant Accounting Policies Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									$ 174,293,000	$ 309,001,000	$ 119,225,000
WEIGHTED AVERAGE NUMBER OF COMMON SHARES OUTSTANDING — BASIC									34,605	34,526	36,048
Weighted Average Number Diluted Shares Outstanding Adjustment									1,174	663	415
WEIGHTED AVERAGE NUMBER OF COMMON SHARES OUTSTANDING — DILUTED									35,779	35,189	36,463
NET INCOME PER COMMON SHARE — BASIC	$ 1.52	$ 1.02	$ 1.51	$ 0.98	$ 3.98	$ 3.05	$ 1.16	$ 0.80	$ 5.04	$ 8.95	$ 3.31
Dilutive Securities, Effect on Basic Earnings Per Share									$ (0.17)	$ 0.17	$ (0.04)
NET INCOME PER COMMON SHARE — DILUTED	$ 1.48	$ 1	$ 1.46	$ 0.93	$ 3.85	$ 2.99	$ 1.14	$ 0.79	$ 4.87	$ 8.78	$ 3.27
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount									0	4,366	7,656
Warrant [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Class of Warrant or Right, Outstanding	0				6,534				0	6,534	7,656
Employee Stock Option [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount									19	110	211

Summary of Significant Accoun45

Summary of Significant Accounting Policies Goodwill (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Abstract]
Goodwill	$ 16	$ 16.2

Summary of Significant Accoun46

Summary of Significant Accounting Policies ASC 606 (Details) - USD ($) $ in Thousands	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts Receivable, Net	$ 203,250	$ 216,293	$ 228,464
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent	42,220	84,582	149,532
Taxes Payable	13,697	14,881	$ 10,660
Deferred Revenue	(398,966)	(616,813)
Retained Earnings (Accumulated Deficit)	(1,410,349)	(1,249,091)
Accounts Receivable [Member] | Static Fixed Fee Agreements [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	6,000
Accounts Receivable [Member] | Static Prepayments [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	0
Accounts Receivable [Member] | Quarter Lag Reporting [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	10,957
Accounts Receivable [Member] | Significant Financing Component [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	0
Accounts Receivable [Member] | Related Tax Effect and Other Balance Sheet Impact [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	(30,000)
Deferred Tax Asset [Domain] | Static Fixed Fee Agreements [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	0
Deferred Tax Asset [Domain] | Static Prepayments [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	0
Deferred Tax Asset [Domain] | Quarter Lag Reporting [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	0
Deferred Tax Asset [Domain] | Significant Financing Component [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	0
Deferred Tax Asset [Domain] | Related Tax Effect and Other Balance Sheet Impact [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	(42,362)
Taxes Payable [Domain] | Static Fixed Fee Agreements [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	0
Taxes Payable [Domain] | Static Prepayments [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	0
Taxes Payable [Domain] | Quarter Lag Reporting [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	0
Taxes Payable [Domain] | Significant Financing Component [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	0
Taxes Payable [Domain] | Related Tax Effect and Other Balance Sheet Impact [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	(1,184)
Deferred Revenue [Domain] | Static Fixed Fee Agreements [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	99,466
Deferred Revenue [Domain] | Static Prepayments [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	85,146
Deferred Revenue [Domain] | Quarter Lag Reporting [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	0
Deferred Revenue [Domain] | Significant Financing Component [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	3,235
Deferred Revenue [Domain] | Related Tax Effect and Other Balance Sheet Impact [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	30,000
Retained Earnings [Member] | Static Fixed Fee Agreements [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	(105,466)
Retained Earnings [Member] | Static Prepayments [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	(85,146)
Retained Earnings [Member] | Quarter Lag Reporting [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	(10,957)
Retained Earnings [Member] | Significant Financing Component [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	(3,235)
Retained Earnings [Member] | Related Tax Effect and Other Balance Sheet Impact [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 43,546
Fixed-Fee Agreements [Domain] | ASC 605 [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Revenue, Revenue Recognized		307,142
Deferred Revenue To Be Recognized Year 2		210,128
Deferred Revenue To Be Recognized Year 3		2,618
Deferred Revenue To Be Recognized Year 4		1,760
Deferred Revenue To Be Recognized Year 5		1,245
Deferred Revenue To Be Recognized Thereafter		2,133
Deferred Revenue To Be Recognized Total		525,026
Dynamic Fixed-Fee Agreements [Domain] | ASC 606 [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Revenue, Revenue Recognized		184,272
Deferred Revenue To Be Recognized Year 2		93,237
Deferred Revenue To Be Recognized Year 3		69,047
Deferred Revenue To Be Recognized Year 4		45,769
Deferred Revenue To Be Recognized Year 5		0
Deferred Revenue To Be Recognized Thereafter		0
Deferred Revenue To Be Recognized Total		392,325
Other [Domain] | ASC 606 [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Revenue To Be Recognized Total		$ 6,700

Significant Agreements Signific

Significant Agreements Significant Events (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Revenues	$ 205,304	$ 97,325	$ 135,779	$ 94,530	$ 273,868	$ 208,307	$ 75,915	$ 107,764	$ 532,938	$ 665,854	$ 441,435

Significant Agreements Revenue

Significant Agreements Revenue Agreements (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Revenues	$ 205,304	$ 97,325	$ 135,779	$ 94,530	$ 273,868	$ 208,307	$ 75,915	$ 107,764	$ 532,938	$ 665,854	$ 441,435
LG [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Revenues									42,400
Patent License Agreement 2017 - A [Domain]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Finite-Lived Patents, Gross	19,700								19,700
Patent License Agreement 2017 - B [Domain]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Finite-Lived Patents, Gross	$ 12,800								$ 12,800
Past Patent Royalties [Member] | LG [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Revenues										34,500
Past Patent Royalties [Member] | Apple [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Revenues										$ 141,400

Geographic Concentration (Detai

Geographic Concentration (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries	$ 205,304	$ 97,325	$ 135,779	$ 94,530	$ 273,868	$ 208,307	$ 75,915	$ 107,764	$ 532,938	$ 665,854	$ 441,435
Apple [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Entity-Wide Revenues, Major Customer, Percentage									0.2097	0.2543	0
Pegatron [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Entity-Wide Revenues, Major Customer, Percentage									< 10%	0.2	0.31
Huawei [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Entity-Wide Revenues, Major Customer, Percentage									0.1434	0.2324	0
Samsung Electronics, Ltd. [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Entity-Wide Revenues, Major Customer, Percentage									0.1295	.1036	0.16
Blackberry [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Entity-Wide Revenues, Major Customer, Percentage									0.13	< 10%	< 10%
Sony Corporation of America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Entity-Wide Revenues, Major Customer, Percentage									< 10%	< 10%	0.14
KOREA
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries									$ 113,059	$ 69,000	$ 69,000
JAPAN
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries									25,210	27,685	53,775
SWEDEN
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries									6,935	6,934	6,934
CANADA
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries									74,107	10,719	13,151
Canada, UK, and South Korea [Domain]
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Long-Lived Assets in Entity's Country of Domicile	300				100				300	100	100
TAIWAN
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries									36,051	185,645	218,584
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries									194,184	199,928	65,703
UNITED STATES | Property Plant and Equipment and Patents, net [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Long-Lived Assets in Entity's Country of Domicile	$ 336,100				$ 287,200				336,100	287,200	289,700
GERMANY
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries									1,892	6,463	6,712
CHINA
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries									77,087	154,767	2,768
Other Europe [Domain]
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries									4,413	4,713	4,807
Other Asia [Domain]
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries									0	0	1
Past Patent Royalties [Member] | Sony Corporation of America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries											$ 21,900
Past Patent Royalties [Member] | Apple [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries										141,400
Past Patent Royalties [Member] | Huawei [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries									8,400	$ 121,500
Past Patent Royalties [Member] | Blackberry [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries									$ 70,700

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Building and improvements	$ 3,624	$ 3,576
Engineering and test equipment	4,034	3,767
Computer Equipment And Software Gross	20,003	18,480
Furniture and fixtures	1,279	1,247
Leasehold improvements	9,711	9,692
Property and equipment, gross	38,651	36,762
Less: accumulated depreciation	(27,978)	(24,136)
Property and equipment, net	10,673	12,626
Depreciation	3,900	4,100	$ 3,800
Capitalized Computer Software, Amortization	500	1,000	1,400
Capitalized Computer Software, Accumulated Amortization	8,800	8,400
Capitalized Computer Software, Net	$ 500	$ 1,000
Sale Leaseback Transaction, Historical Cost			4,500
Sale Leaseback Transaction, Cumulative Gain Recognized			$ 3,400
Building [Member]
Property, Plant and Equipment [Line Items]
Useful Life, Minimum	25 years
Minimum [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Useful Life, Minimum	3 years
Minimum [Member] | Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Useful Life, Minimum	5 years
Maximum [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Useful Life, Minimum	5 years
Maximum [Member] | Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Useful Life, Minimum	10 years

Obligations (Details)

Obligations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2015	Sep. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2011
Debt Instrument [Line Items]
Payments of Debt Issuance Costs			$ 0	$ 0	$ 9,403
Amortization of Financing Costs			1,390	1,716	$ 2,485
Debt Instrument, Unamortized Discount			(27,863)	(39,578)
Deferred Finance Costs, Gross			(3,011)	(4,401)
Long-term Debt			285,126	272,021
Long-term Debt, Current Maturities			0	0
LONG-TERM DEBT			285,126	272,021
Land and Building Carrying Amount			10,673	12,626
2013 - Long Term Debt Maturities			0
2014 - Long Term Debt Maturities			0
2015 - Long Term Debt Maturities			316,000
2016 - Long Term Debt Maturities			0
Thereafter - Long Term Debt Maturities			0
Total debt obligations			316,000
Convertible Debt [Member]
Debt Instrument [Line Items]
Payments of Debt Issuance Costs	$ 9,300
Balance Sheet by Location [Domain] | Convertible Debt [Member]
Debt Instrument [Line Items]
Payments of Debt Issuance Costs						$ 8,000
Convertible Notes 2020 [Member] | Convertible Notes 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 316,000		$ 316,000	$ 316,000
2014 Repurchase Program [Domain]
Debt Instrument [Line Items]
Accelerated Share Repurchases, Initial Price Paid Per Share		$ 53.61

Obligations Senior Convertible

Obligations Senior Convertible Note, Note Hedge and Warrant Transaction (Details)	1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	Apr. 24, 2012USD ($)	Mar. 31, 2015USD ($)	Sep. 30, 2015USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / shares	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2011USD ($)	Sep. 30, 2016shares	Aug. 05, 2016$ / shares	Mar. 11, 2015USD ($)$ / shares	Mar. 09, 2015shares	Mar. 05, 2015USD ($)shares	Apr. 04, 2011USD ($)	Mar. 30, 2011shares	Mar. 29, 2011USD ($)shares
Debt Instrument [Line Items]
Proceeds from (Payments for) Other Financing Activities				$ 0	$ 0	$ (59,376,000)
Shares, Issued | shares								23,667
Proceeds from Issuance of Warrants				0	0	42,881,000
Senior Notes				285,126,000	272,021,000								$ 230,000,000
Payments of Debt Issuance Costs				0	0	9,403,000
Debt Instrument, Interest Rate, Effective Percentage										5.89%			7.00%
Interest Expense, Debt, Excluding Amortization				4,740,000	6,178,000	9,568,000
Accretion of debt discount				(11,715,000)	(13,536,000)	(18,384,000)
Amortization of Financing Costs				1,390,000	1,716,000	2,485,000
Senior Convertible Note, Note Hedge, and Warrant Transaction Interest Expense				17,845,000	21,430,000	30,437,000
Payments of Financing Costs						$ (2,430,000)
Note Warrant2 [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Warrants		$ 5,600,000
Convertible Note Hedge 1 [Member]
Debt Instrument [Line Items]
Proceeds from (Payments for) Other Financing Activities	$ 42,700,000	51,700,000
Convertible Note Hedge 2 [Member]
Debt Instrument [Line Items]
Proceeds from (Payments for) Other Financing Activities		7,700,000
Convertible Note Hedge [Member]
Debt Instrument [Line Items]
Proceeds from (Payments for) Other Financing Activities		59,400,000
Convertible Note/ Hedge Warrant, net [Member]
Debt Instrument [Line Items]
Proceeds from (Payments for) Other Financing Activities		16,500,000					$ 10,900,000
Class of Warrant or Right [Domain]
Debt Instrument [Line Items]
Proceeds from Issuance of Warrants		37,300,000
Convertible Debt [Member]
Debt Instrument [Line Items]
Senior Notes				316,000,000	316,000,000
Payments of Debt Issuance Costs		$ 9,300,000
Convertible Debt [Member] | Convertible Notes 2016 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage													2.50%
Convertible Debt [Member] | Convertible Notes 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage										1.50%
Debt Instrument, Convertible, Conversion Ratio		13.8664
Debt Conversion, Converted Instrument, Amount		$ 1,000
Debt Instrument, Convertible, Conversion Price | $ / shares										$ 72.12
Convertible Notes 2020 [Member] | Convertible Notes 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		316,000,000		$ 316,000,000	$ 316,000,000
Convertible Debt 1 [Member]
Debt Instrument [Line Items]
Senior Notes												$ 275,000,000			$ 200,000,000
Convertible Note Overallotment [Member]
Debt Instrument [Line Items]
Senior Notes												$ 41,000,000			$ 30,000,000
Equity [Member] | Convertible Debt [Member]
Debt Instrument [Line Items]
Class of Warrant or Right, Outstanding | shares											600,000	3,800,000		500,000	3,500,000
Warrant Option Strike Price | $ / shares				$ 88.03					$ 62.95
Senior Notes										$ 59,300,000			$ 43,000,000
Senior Convertible Notes [Equity net of tax]										38,600,000			28,000,000
Payments of Debt Issuance Costs							1,500,000
Payments of Financing Costs			$ 2,400,000
Balance Sheet by Location [Domain] | Convertible Debt [Member]
Debt Instrument [Line Items]
Senior Notes										$ 256,700,000
Payments of Debt Issuance Costs							8,000,000
other long-term assets [Member] | Convertible Debt [Member]
Debt Instrument [Line Items]
Payments of Debt Issuance Costs							$ 6,500,000
Other Long-term Liabilities [Member] | Convertible Debt [Member]
Debt Instrument [Line Items]
Senior Notes													$ 187,000,000
Payments of Debt Issuance Costs		$ 7,000,000
2014 Repurchase Program [Domain]
Debt Instrument [Line Items]
Accelerated Share Repurchases, Initial Price Paid Per Share | $ / shares			$ 53.61
Repurchases related to 2020 Notes [Member] | 2014 Repurchase Program [Domain]
Debt Instrument [Line Items]
Stock Repurchased During Period, Shares | shares			800,000

Commitments (Details)

Commitments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Leases, Income Statement [Abstract]
Operating Leases, Rent Expense	$ 3,900	$ 4,200	$ 3,300
2012 - Operating leases	4,784
Operating Leases, Future Minimum Payments, Due in Three Years	4,499
Operating Leases, Future Minimum Payments, Due in Four Years	2,918
Operating Leases, Future Minimum Payments, Due in Four Years	2,377
2016 - Operating leases	2,131
Thereafter - Operating leases	$ 4,741

Compensation Plans and Progra54

Compensation Plans and Programs (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	Jun. 14, 2017	Jun. 13, 2017	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award and Other Compensation Benefits [Line Items] [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross				(25)
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures	(1,162)
Stock Issued During Period, Shares, Share-based Compensation, Forfeited				(22)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value				$ 63.30
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period				(688)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number			1,005	1,005	1,398
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price				$ 85.85
Equity Available for Grant [Roll Forward]
Equity Instruments Available for Grant as of December 31, 2010		1,236		1,236
RSUs granted				(317)
Equity Instruments Available for Grant as of December 31, 2011	1,162		2,403	2,403	1,236
Minimum Exercise Price Per Share Options			100.00%	100.00%
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term				8 years 6 months
Stock Options, Outstanding [Roll Forward]
Outstanding Options, as of December 31, 2010		515		515
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period				0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period				(9)
Outstanding Options, as of December 31, 2011			531	531	515
Weighted Average Excercise Price, as of December 31, 2010		$ 37.38		$ 37.38
Cancellations in Period, Weighted Average Exercise Price				0
Exercises in Period, Weighted Average Exercise Price				44.20
Weighted Average Exercise Price, as of December 31, 2011			$ 39.55	39.55	$ 37.38
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit				9
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit				$ 11.63
Intrinsic Value of Stock Options Exercised During Period				$ 300	$ 1,500	$ 200
Stock Options, Outstanding, Intrinsic Value			$ 19,700	19,700
Proceeds from Stock Options Exercised				382	485	46
Excess Tax Benefit from Share-based Compensation, Financing Activities				0	625	2,457
Vested in Period, Total Fair Value				$ 56,000	9,800	$ 26,300
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options			500	500
Proceeds From Stock Options If Exercised			$ 21,200	$ 21,200	$ 19,400
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
RSUs granted				(317)
RSUs, Grants in Period, Weighted Average Grant Date Fair Value				$ 58.63	$ 44.08	$ 41.29
RSUs, Vested in Period, Weighted Average Grant Date Fair Value				$ 35.14
Incremental Common Shares Attributable to Participating Nonvested Shares with Non-forfeitable Dividend Rights				100
Share-based Compensation				$ 18,062	$ 21,840	$ 15,139
Other than Temporary Impairment Losses, Investments					200
Other Postretirement Benefits Cost (Reversal of Cost)				$ 300	$ 500	200
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value			$ 57.95	$ 57.95	$ 46.65
Stock Options Outstaning which have an Indefinite Contractual Term [Member]
Stock Options, Outstanding [Roll Forward]
Outstanding Options, as of December 31, 2011			100	100
Cash from stock options [Member]
Stock Options, Outstanding [Roll Forward]
Proceeds from Stock Options Exercised				$ 400
Restricted Stock Units (RSU) and/or Restricted Stock [Member]
Equity Available for Grant [Roll Forward]
RSUs granted				(200)	(400)
Stock Options, Outstanding [Roll Forward]
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized			$ 13,600	$ 13,600	$ 24,800
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
RSUs granted				(200)	(400)
401(k) and Profit Sharing [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Defined Benefit Plan, Plan Assets, Contributions by Employer				$ 1,400	$ 1,100	$ 1,200
2009 Plan [Domain]
Share-based Compensation Arrangement by Share-based Payment Award and Other Compensation Benefits [Line Items] [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross		(25)
Equity Available for Grant [Roll Forward]
RSUs granted		(295)
Options Expired and RSUs cancelled		246
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
RSUs granted		(295)
Prior Plan [Domain] | Stock Options Outstaning which have an Indefinite Contractual Term [Member]
Stock Options, Outstanding [Roll Forward]
Outstanding Options, as of December 31, 2011			100	100
2017 Plan [Domain]
Equity Available for Grant [Roll Forward]
RSUs granted			(8)
Options Expired and RSUs cancelled			11
Number of Shares Authorized	2,400
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
RSUs granted			(8)

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended			144 Months Ended
	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Jan. 01, 2018	Dec. 31, 2014
Income Tax Contingency [Line Items]
Additions			$ 3,209	$ 141
Excess Tax Benefit from Share-based Compensation, Financing Activities		$ 0	625	2,457
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation				2,457
Federal		3,656	14,637	42,181
State		(1)	(60)	415
Foreign source withholding tax		47,592	79,932	55,276
Current Income Tax Expense (Benefit)		51,247	94,509	97,872
Federal		21,671	(48,086)	(89,026)
State		(1,074)	(557)	554
Foreign source withholding tax		49,832	70,925	55,221
Deferred income taxes		$ 70,429	$ 22,282	$ (33,251)
Income Tax Expense (Benefit)		41.60%	27.70%	35.70%
Net operating losses		$ 301,495	$ 437,306	$ 208,549
Deferred Tax Assets, Operating Loss Carryforwards		125,156	89,625		$ 125,156
Deferred revenue, net		38,282	92,294		38,282
Stock compensation		8,936	14,686		8,936
Patent amortization		16,059	24,145		16,059
Deferred Tax Asset Depreciation		(279)	(572)		(279)
Deferred Tax Asset OTTI		450	619		450
Other accrued liabilities		242	4,804		242
Other employee benefits		4,098	2,799		4,098
Deferred Tax Assets Net Before Deducting Valuation Allowance		192,944	228,400		192,944
Less: valuation allowance		123,916	89,815		123,916
Net deferred tax asset		$ 69,028	$ 138,585		69,028
Tax at U.S. statutory rate		35.00%	35.00%	35.00%
State		0.00%	(0.10%)	0.50%
Change in federal and state valuation allowance		0.50%	0.10%	0.00%
Adjustment to tax credits		(0.80%)	(0.50%)	(1.20%)
Adjustments to uncertain tax positions		(2.40%)	2.10%	0.00%
Permanent differences		1.00%	0.60%	1.20%
Effective Income Tax Rate Reconciliation, Deduction, Qualified Production Activity, Percent		(2.00%)	(9.80%)	0.00%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Percent		(4.00%)	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent		14.60%	0.00%	0.00%
Other		(0.30%)	0.30%	0.20%
Deferred Tax Assets, Tax Credit Carryforwards, Research			$ 100
Unrecognized Tax Benefits, Decreases Resulting from Prior Period Tax Positions	$ 600	$ (6,544)	(562)	$ 0
Unrecognized Tax Benefits, Increases Resulting from Prior Period Tax Positions		0	6,281	0
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		3,252	10,397	1,469	3,252		$ 1,361
Reductions		0	0	0
Unrecognized Tax Benefits, Decreases Resulting from Prior Period Tax Positions			0	(33)
Settlements	$ 600	(6,544)	(562)	0
Lapses in statues of limitations		0	0	0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued		100			100
Income taxes paid, including foreign witholding taxes		66,793	108,635	85,780
Taxes Payable		14,881	10,660		14,881	$ 13,697
Federal
Income Tax Contingency [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Domestic		1,804	0		1,804
Deferred revenue, net		9,058	60,320		9,058
Stock compensation		6,643	12,648		6,643
Patent amortization		16,052	24,145		16,052
Deferred Tax Asset Depreciation		(214)	(502)		(214)
Deferred Tax Asset OTTI		379	558		379
Other accrued liabilities		268	4,483		268
Other employee benefits		3,449	2,524		3,449
Deferred Tax Assets Net Before Deducting Valuation Allowance		37,439	104,176		37,439
Less: valuation allowance		1,773	0		1,773
Net deferred tax asset		35,666	104,176		35,666
State
Income Tax Contingency [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, State and Local		122,364	89,162		122,364
Deferred Tax Assets, Operating Loss Carryforwards, State and Local		1,600,000			1,600,000
Deferred revenue, net		35	288		35
Stock compensation		2,293	2,038		2,293
Patent amortization		7	0		7
Deferred Tax Asset Depreciation		(65)	(70)		(65)
Deferred Tax Asset OTTI		71	61		71
Other accrued liabilities		(26)	321		(26)
Other employee benefits		649	275		649
Deferred Tax Assets Net Before Deducting Valuation Allowance		125,328	92,075		125,328
Less: valuation allowance		121,155	89,352		121,155
Net deferred tax asset		4,173	2,723		4,173
Unrecognized Tax Benefits			11,900
Research and Development Arrangement [Member]
Income Tax Contingency [Line Items]
Additions		1,000
Unrecognized Tax Benefits, Decreases Resulting from Prior Period Tax Positions		(6,500)
Foreign
Income Tax Contingency [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Foreign		988	463		988
Deferred revenue, net		29,189	31,686		29,189
Stock compensation		0	0		0
Patent amortization		0	0		0
Deferred Tax Asset Depreciation		0	0		0
Deferred Tax Asset OTTI		0	0		0
Other accrued liabilities		0	0		0
Other employee benefits		0	0		0
Deferred Tax Assets Net Before Deducting Valuation Allowance		30,177	32,149		30,177
Less: valuation allowance		988	463		988
Net deferred tax asset		29,189	31,686		29,189
Income taxes paid, including foreign witholding taxes		46,700	$ 79,900	$ 55,300	422,300
Tax Year 2016 [Member] | Research and Development Arrangement [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits, Decreases Resulting from Prior Period Tax Positions		1,600
2011-2015 [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits, Decreases Resulting from Prior Period Tax Positions		8,000
Settlements		$ 8,000
ForeignGovenmentswithUSTaxTreaties [Domain] | Foreign
Income Tax Contingency [Line Items]
Income taxes paid, including foreign witholding taxes					$ 275,200

Income Taxes Income Taxes (Deta

Income Taxes Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 3,252	$ 10,397	$ 1,469	$ 1,361
Income Tax Expense (Benefit)	121,676	$ 116,791	$ 64,621
2017 Income Tax Reform [Domain]
Income Tax Contingency [Line Items]
Income Tax Expense (Benefit)	$ 42,600

Equity Transactions Share Repur

Equity Transactions Share Repurchases (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended									6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Mar. 31, 2015	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Aug. 05, 2016	Mar. 09, 2015	Mar. 05, 2015	Mar. 30, 2011	Mar. 29, 2011
Accelerated Share Repurchases [Line Items]
Common Stock, Dividends, Per Share, Declared	$ 0.35	$ 0.35	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.20	$ 0.20						$ 1.30	$ 1	$ 0.80
Dividends, Common Stock, Cash	$ 12,156	$ 12,149	$ 10,413	$ 10,404	$ 10,290	$ 10,285	$ 6,861	$ 6,923		$ 20,817	$ 13,784	$ 32,966	$ 24,069	$ 45,122	$ 34,359
Proceeds from Issuance of Warrants														$ 0	$ 0	$ 42,881
Shares, Issued						23,667							23,667
Note Warrant2 [Member]
Accelerated Share Repurchases [Line Items]
Proceeds from Issuance of Warrants									$ 5,600
Class of Warrant or Right [Domain]
Accelerated Share Repurchases [Line Items]
Proceeds from Issuance of Warrants									$ 37,300
2014 Repurchase Program [Member]
Accelerated Share Repurchases [Line Items]
Stock Repurchased During Period, Shares														107,000	1,304,000	1,836,000	3,554,000
Stock Repurchased During Period, Value														$ 7,693	$ 64,685	$ 96,410	$ 152,625
Equity [Member] | Convertible Debt [Member]
Accelerated Share Repurchases [Line Items]
Class of Warrant or Right, Outstanding																			600,000	3,800,000	500,000	3,500,000
Warrant Option Strike Price	$ 88.03													$ 88.03				$ 62.95

Equity Transactions Common Stoc

Equity Transactions Common Stock Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Aug. 05, 2016	Mar. 09, 2015	Mar. 05, 2015	Mar. 30, 2011	Mar. 29, 2011
Class of Warrant or Right [Line Items]
Proceeds from Issuance of Warrants		$ 0	$ 0	$ 42,881
Equity [Member] | Convertible Debt [Member]
Class of Warrant or Right [Line Items]
Class of Warrant or Right, Outstanding						0.6	3.8	0.5	3.5
Warrant Option Strike Price		$ 88.03			$ 62.95
Note Warrant2 [Member]
Class of Warrant or Right [Line Items]
Proceeds from Issuance of Warrants	$ 5,600
Class of Warrant or Right [Domain]
Class of Warrant or Right [Line Items]
Proceeds from Issuance of Warrants	$ 37,300

Equity Transactions Dividends (

Equity Transactions Dividends (Details) - $ / shares	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Dividends Payable [Line Items]
Common Stock, Dividends, Per Share, Declared	$ 0.35	$ 0.35	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.20	$ 0.20	$ 1.30	$ 1	$ 0.80

Selected Quarterly Results (Det

Selected Quarterly Results (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effect of Fourth Quarter Events [Line Items]
Other than Temporary Impairment Losses, Investments										$ 200
Revenues	$ 205,304	$ 97,325	$ 135,779	$ 94,530	$ 273,868	$ 208,307	$ 75,915	$ 107,764	$ 532,938	665,854	$ 441,435
NET INCOME	$ 52,502	$ 35,536	$ 52,499	$ 33,756	$ 136,470	$ 104,466	$ 39,994	$ 28,071	$ 170,714	$ 305,480	$ 116,394
NET INCOME PER COMMON SHARE — BASIC	$ 1.52	$ 1.02	$ 1.51	$ 0.98	$ 3.98	$ 3.05	$ 1.16	$ 0.80	$ 5.04	$ 8.95	$ 3.31
NET INCOME PER COMMON SHARE — DILUTED	$ 1.48	$ 1	$ 1.46	$ 0.93	$ 3.85	$ 2.99	$ 1.14	$ 0.79	$ 4.87	$ 8.78	$ 3.27
Past Infringement [Member]
Effect of Fourth Quarter Events [Line Items]
Royalty Revenue									$ 162,900	$ 309,700

VIE (Details)

VIE (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Net Income (Loss) Attributable to Noncontrolling Interest	$ (3,579)	$ (3,521)	$ (2,831)
Assets [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	34,400	28,900
Cash and Cash Equivalents [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	23,300	20,300
Patents [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	11,100	8,000
Liabilities, Total [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	$ 200	$ 2,300

Business Combinations (Details)

Business Combinations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Revenues	$ 205,304	$ 97,325	$ 135,779	$ 94,530	$ 273,868	$ 208,307	$ 75,915	$ 107,764	$ 532,938	$ 665,854	$ 441,435
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									174,293	309,001	119,225
Business Acquisition, Pro Forma Revenue										672,695	451,853
Business Acquisition, Pro Forma Net Income (Loss)										305,237	109,834
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets	2,221								2,221
Payments to Acquire Businesses, Net of Cash Acquired									0	48,000	$ 0
Cash Acquired from Acquisition										$ 400
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	(8,754)								(8,754)
Goodwill, Gross	16,033								16,033
Customer Relationships [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	1,700								1,700
Patented Technology [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	36,200								36,200
Trade Names [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	$ 600								$ 600
Customer Relationships [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life									10 years
Trade Names [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life									9 years

Other Expense Income (Details)

Other Expense Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest expense	$ (17,845)	$ (21,126)	$ (30,417)
Interest and investment income	8,488	3,748	3,858
Other	$ 252	$ 2,343	$ (975)