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	$ 0us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_BIOkeyMember	$ 0.1us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_BIOkeyMember
Investment Owned, Balance, Shares	1.4us-gaap_InvestmentOwnedBalanceShares / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_BIOkeyMember		4.0us-gaap_InvestmentOwnedBalanceShares / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_BIOkeyMember
Investment Owned, at Fair Value	0.2us-gaap_InvestmentOwnedAtFairValue / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_BIOkeyMember		0.5us-gaap_InvestmentOwnedAtFairValue / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_BIOkeyMember
DDD [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	0us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_DDDMember	0us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_DDDMember
Investment Owned, Balance, Shares				7.0us-gaap_InvestmentOwnedBalanceShares / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = idcc_DDDMember
Investment Owned, at Fair Value				$ 0.9us-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: