v2.4.1.9

Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2013 | Sep. 30, 2013
BIO-key [Member] |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Related Party Transaction, Expenses from Transactions with Related Party | $ 0 us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_BIOkeyMember | $ 0.1 us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_BIOkeyMember |  |
Investment Owned, Balance, Shares | 1.4 us-gaap_InvestmentOwnedBalanceShares / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_BIOkeyMember |  | 4.0 us-gaap_InvestmentOwnedBalanceShares / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_BIOkeyMember |
Investment Owned, at Fair Value | 0.2 us-gaap_InvestmentOwnedAtFairValue / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_BIOkeyMember |  | 0.5 us-gaap_InvestmentOwnedAtFairValue / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_BIOkeyMember |
DDD [Member] |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Related Party Transaction, Expenses from Transactions with Related Party | 0 us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_DDDMember | 0 us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_DDDMember |  |
Investment Owned, Balance, Shares |  |  |  | 7.0 us-gaap_InvestmentOwnedBalanceShares / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_DDDMember
Investment Owned, at Fair Value |  |  |  | $ 0.9 us-gaap_InvestmentOwnedAtFairValue / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_DDDMember

X
- Definition Value of the investment at close of period. For schedules of investments that are categorized, the value would be aggregated by category. For investment in and advances to affiliates, if operations of any controlled companies are different in character from those of the company, group such affiliates within divisions and by type of activities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 13 -Paragraph Column C -Article 12 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 14 -Paragraph Column E -Article 12 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12.Column C.3,4) -URI http://asc.fasb.org/extlink&oid=34726532&loc=d3e611133-123010 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 4 -Subparagraph (SX 210.12-12C.Column C.7) -URI http://asc.fasb.org/extlink&oid=34726532&loc=d3e611225-123010 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14.Column E.2,3) -URI http://asc.fasb.org/extlink&oid=34726532&loc=d3e611322-123010 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 5 -Subparagraph (SX 210.12-13.Column C.6) -URI http://asc.fasb.org/extlink&oid=34726532&loc=d3e611282-123010 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12 -Paragraph Column C -Article 12 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12 -Paragraph 3, 4 -Article 12 Reference 9: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 14 -Paragraph 2, 3 -Article 12 Reference 10: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 13 -Paragraph 6 -Article 12 Reference 11: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12C -Paragraph 7 -Article 12 Reference 12: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12C -Paragraph Column C -Article 12 + Details
Name: | us-gaap_InvestmentOwnedAtFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Balance held at close of period in number of shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 4 -Subparagraph (SX 210.12-12C.Column B) -URI http://asc.fasb.org/extlink&oid=34726532&loc=d3e611225-123010 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14.Column B) -URI http://asc.fasb.org/extlink&oid=34726532&loc=d3e611322-123010 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12.Column B) -URI http://asc.fasb.org/extlink&oid=34726532&loc=d3e611133-123010 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12C -Paragraph Column B -Article 12 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12 -Paragraph Column B -Article 12 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 14 -Paragraph Column B -Article 12 + Details
Name: | us-gaap_InvestmentOwnedBalanceShares
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864 + Details
Name: | us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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

X
- Details
Name: | us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=idcc_BIOkeyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=idcc_DDDMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |