v2.4.1.9

Equity Transactions Share Repurchases (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended			34 Months Ended	3 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2014	Jun. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Jun. 30, 2012	Mar. 31, 2009
Accelerated Share Repurchases [Line Items]
Stock Repurchased During Period, Shares													3,554us-gaap_StockRepurchasedDuringPeriodShares	917us-gaap_StockRepurchasedDuringPeriodShares	4,838us-gaap_StockRepurchasedDuringPeriodShares	1,012us-gaap_StockRepurchasedDuringPeriodShares
Stock Repurchased During Period, Value													$ 152,625,000us-gaap_StockRepurchasedDuringPeriodValue	$ 29,135,000us-gaap_StockRepurchasedDuringPeriodValue	$ 152,694,000us-gaap_StockRepurchasedDuringPeriodValue	$ 25,000,000us-gaap_StockRepurchasedDuringPeriodValue
Common Stock, Dividends, Per Share, Declared	$ 0.20us-gaap_CommonStockDividendsPerShareDeclared	$ 0.20us-gaap_CommonStockDividendsPerShareDeclared	$ 0.20us-gaap_CommonStockDividendsPerShareDeclared	$ 0.10us-gaap_CommonStockDividendsPerShareDeclared	$ 0.10us-gaap_CommonStockDividendsPerShareDeclared	$ 0.10us-gaap_CommonStockDividendsPerShareDeclared	$ 0.10us-gaap_CommonStockDividendsPerShareDeclared	$ 0.10us-gaap_CommonStockDividendsPerShareDeclared					$ 0.70us-gaap_CommonStockDividendsPerShareDeclared	$ 0.40us-gaap_CommonStockDividendsPerShareDeclared	$ 1.90us-gaap_CommonStockDividendsPerShareDeclared
Dividends, Common Stock, Cash	7,500,000us-gaap_DividendsCommonStockCash	7,666,000us-gaap_DividendsCommonStockCash	8,033,000us-gaap_DividendsCommonStockCash	3,954,000us-gaap_DividendsCommonStockCash	4,031,000us-gaap_DividendsCommonStockCash	4,119,000us-gaap_DividendsCommonStockCash	4,118,000us-gaap_DividendsCommonStockCash	4,115,000us-gaap_DividendsCommonStockCash	11,987,000us-gaap_DividendsCommonStockCash	8,233,000us-gaap_DividendsCommonStockCash	19,653,000us-gaap_DividendsCommonStockCash	12,352,000us-gaap_DividendsCommonStockCash	27,153,000us-gaap_DividendsCommonStockCash	16,383,000us-gaap_DividendsCommonStockCash
Note Warrant [Member]
Accelerated Share Repurchases [Line Items]
Proceeds from Issuance of Warrants																	27,600,000us-gaap_ProceedsFromIssuanceOfWarrants / us-gaap_DebtInstrumentAxis = us-gaap_NoteWarrantMember
Note Warrant2 [Member]
Accelerated Share Repurchases [Line Items]
Proceeds from Issuance of Warrants																	4,100,000us-gaap_ProceedsFromIssuanceOfWarrants / us-gaap_DebtInstrumentAxis = idcc_NoteWarrant2Member
2009 Repurchase Program [Domain]
Accelerated Share Repurchases [Line Items]
Stock Repurchased During Period, Shares													0us-gaap_StockRepurchasedDuringPeriodShares / us-gaap_ShareRepurchaseProgramAxis = idcc_A2009RepurchaseProgramDomain	0us-gaap_StockRepurchasedDuringPeriodShares / us-gaap_ShareRepurchaseProgramAxis = idcc_A2009RepurchaseProgramDomain	2,286us-gaap_StockRepurchasedDuringPeriodShares / us-gaap_ShareRepurchaseProgramAxis = idcc_A2009RepurchaseProgramDomain	1,012us-gaap_StockRepurchasedDuringPeriodShares / us-gaap_ShareRepurchaseProgramAxis = idcc_A2009RepurchaseProgramDomain
Stock Repurchased During Period, Value													0us-gaap_StockRepurchasedDuringPeriodValue / us-gaap_ShareRepurchaseProgramAxis = idcc_A2009RepurchaseProgramDomain	0us-gaap_StockRepurchasedDuringPeriodValue / us-gaap_ShareRepurchaseProgramAxis = idcc_A2009RepurchaseProgramDomain	75,000,000us-gaap_StockRepurchasedDuringPeriodValue / us-gaap_ShareRepurchaseProgramAxis = idcc_A2009RepurchaseProgramDomain	25,000,000us-gaap_StockRepurchasedDuringPeriodValue / us-gaap_ShareRepurchaseProgramAxis = idcc_A2009RepurchaseProgramDomain
2012 Repurchase Program [Domain]
Accelerated Share Repurchases [Line Items]
Stock Repurchased During Period, Shares													0us-gaap_StockRepurchasedDuringPeriodShares / us-gaap_ShareRepurchaseProgramAxis = idcc_A2012RepurchaseProgramDomain	917us-gaap_StockRepurchasedDuringPeriodShares / us-gaap_ShareRepurchaseProgramAxis = idcc_A2012RepurchaseProgramDomain	2,552us-gaap_StockRepurchasedDuringPeriodShares / us-gaap_ShareRepurchaseProgramAxis = idcc_A2012RepurchaseProgramDomain	0us-gaap_StockRepurchasedDuringPeriodShares / us-gaap_ShareRepurchaseProgramAxis = idcc_A2012RepurchaseProgramDomain
Stock Repurchased During Period, Value													0us-gaap_StockRepurchasedDuringPeriodValue / us-gaap_ShareRepurchaseProgramAxis = idcc_A2012RepurchaseProgramDomain	29,135,000us-gaap_StockRepurchasedDuringPeriodValue / us-gaap_ShareRepurchaseProgramAxis = idcc_A2012RepurchaseProgramDomain	77,694,000us-gaap_StockRepurchasedDuringPeriodValue / us-gaap_ShareRepurchaseProgramAxis = idcc_A2012RepurchaseProgramDomain	0us-gaap_StockRepurchasedDuringPeriodValue / us-gaap_ShareRepurchaseProgramAxis = idcc_A2012RepurchaseProgramDomain
2014 Repurchase Program [Member]
Accelerated Share Repurchases [Line Items]
Stock Repurchased During Period, Shares													3,554us-gaap_StockRepurchasedDuringPeriodShares / us-gaap_ShareRepurchaseProgramAxis = idcc_A2014RepurchaseProgramMember	0us-gaap_StockRepurchasedDuringPeriodShares / us-gaap_ShareRepurchaseProgramAxis = idcc_A2014RepurchaseProgramMember	0us-gaap_StockRepurchasedDuringPeriodShares / us-gaap_ShareRepurchaseProgramAxis = idcc_A2014RepurchaseProgramMember	0us-gaap_StockRepurchasedDuringPeriodShares / us-gaap_ShareRepurchaseProgramAxis = idcc_A2014RepurchaseProgramMember
Stock Repurchased During Period, Value													152,625,000us-gaap_StockRepurchasedDuringPeriodValue / us-gaap_ShareRepurchaseProgramAxis = idcc_A2014RepurchaseProgramMember	0us-gaap_StockRepurchasedDuringPeriodValue / us-gaap_ShareRepurchaseProgramAxis = idcc_A2014RepurchaseProgramMember	0us-gaap_StockRepurchasedDuringPeriodValue / us-gaap_ShareRepurchaseProgramAxis = idcc_A2014RepurchaseProgramMember	0us-gaap_StockRepurchasedDuringPeriodValue / us-gaap_ShareRepurchaseProgramAxis = idcc_A2014RepurchaseProgramMember
2012 Repurchase Program [Domain]
Accelerated Share Repurchases [Line Items]
Stock Repurchase Program, Authorized Amount																		200,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1 / us-gaap_StatementClassOfStockAxis = idcc_A2012RepurchaseProgramDomain
2009 Repurchase Program [Domain]
Accelerated Share Repurchases [Line Items]
Stock Repurchase Program, Authorized Amount																			100,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1 / us-gaap_StatementClassOfStockAxis = idcc_A2009RepurchaseProgramDomain
2014 Repurchase Program [Member]
Accelerated Share Repurchases [Line Items]
Stock Repurchase Program, Authorized Amount			$ 300,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1 / us-gaap_StatementClassOfStockAxis = idcc_A2014RepurchaseProgramMember						$ 300,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1 / us-gaap_StatementClassOfStockAxis = idcc_A2014RepurchaseProgramMember

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- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

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- Definition

Amount of paid and unpaid common stock dividends declared with the form of settlement in cash.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

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- Definition

The cash inflow from issuance of rights to purchase common shares at predetermined price (usually issued together with corporate debt).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

-Section 45

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-Subparagraph (a)

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- Definition

Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644



Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-Number 210

-Section 02

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Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3



Reference 2: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Topic 505

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Amount of stock repurchase plan authorized.

+ References

No definition available.

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