v2.4.1.9

VIE (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2014
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Assets [Member] |
Variable Interest Entity [Line Items] |
Variable Interest Entity, Consolidated, Carrying Amount, Assets | $ 15.3 us-gaap_VariableInterestEntityConsolidatedCarryingAmountAssets / idcc_VIEAssetClassAxis = us-gaap_AssetsMember
Cash and Cash Equivalents [Member] |
Variable Interest Entity [Line Items] |
Variable Interest Entity, Consolidated, Carrying Amount, Assets | 11.4 us-gaap_VariableInterestEntityConsolidatedCarryingAmountAssets / idcc_VIEAssetClassAxis = us-gaap_CashAndCashEquivalentsMember
Patents [Member] |
Variable Interest Entity [Line Items] |
Variable Interest Entity, Consolidated, Carrying Amount, Assets | 3.9 us-gaap_VariableInterestEntityConsolidatedCarryingAmountAssets / idcc_VIEAssetClassAxis = us-gaap_PatentsMember
Liabilities, Total [Member] |
Variable Interest Entity [Line Items] |
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities | $ 0.4 us-gaap_VariableInterestEntityConsolidatedCarryingAmountLiabilities / us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis = us-gaap_LiabilitiesTotalMember

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- Definition The carrying amount of the consolidated Variable Interest Entity's assets included in the reporting entity's statement of financial position. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (bb) -URI http://asc.fasb.org/extlink&oid=28200181&loc=d3e5710-111685 + Details
Name: | us-gaap_VariableInterestEntityConsolidatedCarryingAmountAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The carrying amount of the consolidated Variable Interest Entity's liabilities included in the reporting entity's statement of financial position. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (bb) -URI http://asc.fasb.org/extlink&oid=28200181&loc=d3e5710-111685 + Details
Name: | us-gaap_VariableInterestEntityConsolidatedCarryingAmountLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_VariableInterestEntityLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | idcc_VIEAssetClassAxis=us-gaap_AssetsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | idcc_VIEAssetClassAxis=us-gaap_CashAndCashEquivalentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | idcc_VIEAssetClassAxis=us-gaap_PatentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=us-gaap_LiabilitiesTotalMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |