v2.4.0.6

Geographic Concentration (Details) (USD $)	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries	$ 301,742,000		$ 394,545,000		$ 297,404,000
Property and Equipment Held in United States	100.00%		99.00%		99.00%
Samsung Electronics, Ltd. [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue, 10% or More of InterDigital's Total Revenue	34.00%		26.00%		33.00%
Research in Motion Limited [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue, 10% or More of InterDigital's Total Revenue	14.00%
Entity-Wide Revenues, Major Customer, Percentage			< 10%	[1]	< 10%	[1]
HTC Corporation [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue, 10% or More of InterDigital's Total Revenue	11.00%
Entity-Wide Revenues, Major Customer, Percentage			< 10%	[1]	< 10%	[1]
LG Electronics [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue, 10% or More of InterDigital's Total Revenue	0.00%		15.00%		19.00%
Sharp [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue, 10% or More of InterDigital's Total Revenue					10.00%
Entity-Wide Revenues, Major Customer, Percentage	< 10%	[1]	< 10%	[1]
KOREA
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries	118,078,000		175,614,000		160,470,000
JAPAN
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries	61,594,000		121,113,000		73,253,000
CANADA
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries	54,728,000		38,820,000		27,371,000
CANADA | Patents [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Long-Lived Assets in Foreign Countries	100,000		200,000		800,000
TAIWAN
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries	43,993,000		21,559,000		15,336,000
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Entity's Country of Domicile	13,719,000		18,953,000		9,361,000
UNITED STATES | Property and Equipment [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Long-Lived Assets in Entity's Country of Domicile	146,000,000		138,400,000		128,800,000
GERMANY
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries	5,439,000		10,292,000		10,394,000
CHINA
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries	688,000		6,305,000		0
OTHER EUROPE
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries	3,461,000		1,877,000		1,196,000
OTHER ASIA
Revenues from External Customers and Long-Lived Assets [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries	$ 42,000		$ 12,000		$ 23,000
[1] During 2011, 2010, and 2009, the following licensees accounted for 10% or more of total revenues: 2011 2010 2009Samsung Electronics Co., Ltd. 34% 26% 33%Research in Motion Limited14% < 10% < 10%HTC Corporation11% < 10% < 10%LG Electronics0% 15% 19%Sharp Corporation< 10% < 10% 10%

X

- Definition

Percent of revenue generated from a single external customer that accounts for 10 percent or more of an entity's revenues.

+ References

No definition available.

+ Details

Name:	idcc_EntityWideRevenueMajorCustomerPercent
Namespace Prefix:	idcc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Percent of revenue generated from a single external customer that accounts for 10 percent or more of an entity's revenues.

+ References

No definition available.

+ Details

Name:	idcc_EntityWideRevenuesMajorCustomerPercentage
Namespace Prefix:	idcc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Property and Equipment Held in United States

+ References

No definition available.

+ Details

Name:	idcc_PropertyAndEquipmentHeldInUnitedStates
Namespace Prefix:	idcc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Amount of long-lived assets other than financial instruments, long-term customer relationships of a financial institution, mortgage and other servicing rights, deferred policy acquisition costs, and deferred tax assets, located in the entity's country of domicile.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 131

-Paragraph 38

-Subparagraph b(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 280

-SubTopic 10

-Section 50

-Paragraph 41

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e9038-108599

+ Details

Name:	us-gaap_EntityWideDisclosureOnGeographicAreasLongLivedAssetsInEntitysCountryOfDomicile
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount of long-lived assets other than financial instruments, long-term customer relationships of a financial institution, mortgage and other servicing rights, deferred policy acquisition costs, and deferred tax assets, located in foreign countries in total in which the entity holds assets.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 131

-Paragraph 38

-Subparagraph b(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 280

-SubTopic 10

-Section 50

-Paragraph 41

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e9038-108599

+ Details

Name:	us-gaap_EntityWideDisclosureOnGeographicAreasLongLivedAssetsInForeignCountries
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Revenues from external customers attributed to the entity's country of domicile.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 131

-Paragraph 38

-Subparagraph a(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 280

-SubTopic 10

-Section 50

-Paragraph 41

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e9038-108599

+ Details

Name:	us-gaap_EntityWideDisclosureOnGeographicAreasRevenueFromExternalCustomersAttributedToEntitysCountryOfDomicile
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Revenues from external customers attributed to all foreign countries in total from which the entity derives revenues.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 131

-Paragraph 38

-Subparagraph a(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 280

-SubTopic 10

-Section 50

-Paragraph 41

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e9038-108599

+ Details

Name:	us-gaap_EntityWideDisclosureOnGeographicAreasRevenueFromExternalCustomersAttributedToForeignCountries
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Details

Name:	us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration