v2.4.0.6

Summary of Significant Accounting Policies Intangible Assets (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2009
Intangible Assets [Abstract]
Amortization of Acquired Intangible Assets	$ 2.3

X

- Details

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

X

- Definition

The aggregate expense charged against earnings to allocate the cost of acquired intangible assets. As a noncash expense, this element is added back to net income when calculating cash provided by (used in) operations using the indirect method.

+ References

No definition available.

+ Details

Name:	us-gaap_AmortizationOfAcquiredIntangibleAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration