Revision to Noncontrolling Interest (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss attributable to noncontrolling interest									$ (5,977)	$ (5,556)	$ (5,506)
Net income attributable to InterDigital, Inc.	$ 13,754	$ 2,234	$ 7,743	$ (2,803)	$ 2,083	$ 21,752	$ 10,966	$ 30,230	$ 20,928	$ 65,031	$ 176,220
Net income per share — basic (in usd per share)	$ 0.44	$ 0.07	$ 0.25	$ (0.09)	$ 0.06	$ 0.63	$ 0.32	$ 0.87	$ 0.66	$ 1.89	$ 5.09
Net income per share — diluted (in usd per share)	$ 0.44	$ 0.07	$ 0.24	$ (0.09)	$ 0.06	$ 0.61	$ 0.31	$ 0.85	$ 0.66	$ 1.84	$ 4.93
Total comprehensive income attributable to InterDigital, Inc.									$ 23,325	$ 65,092	$ 174,651
Total InterDigital, Inc. shareholders’ equity	$ 761,557				$ 936,729				761,557	936,729
Noncontrolling interest	24,724				1,284				24,724	1,284
Total equity	$ 786,281				938,013				$ 786,281	938,013	873,148	$ 754,368
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss attributable to noncontrolling interest										4,393	3,579
Net income attributable to InterDigital, Inc.					$ 1,830					$ 63,868	$ 174,293
Net income per share — basic (in usd per share)					$ 0.05					$ 1.85	$ 5.04
Net income per share — diluted (in usd per share)					$ 0.05					$ 1.81	$ 4.87
Total comprehensive income attributable to InterDigital, Inc.										$ 63,929	$ 172,724
Retained earnings					$ 1,426,266					1,426,266	1,249,091	1,120,766
Total InterDigital, Inc. shareholders’ equity					927,025					927,025	855,267	739,709
Noncontrolling interest					10,988					10,988	17,881	14,659
Total equity					938,013					938,013	873,148	754,368
As Adjusted
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss attributable to noncontrolling interest										5,556	5,506
Net income attributable to InterDigital, Inc.										$ 65,031	$ 176,220
Net income per share — basic (in usd per share)										$ 1.89	$ 5.09
Net income per share — diluted (in usd per share)										$ 1.84	$ 4.93
Total comprehensive income attributable to InterDigital, Inc.										$ 65,092	$ 174,651
Retained earnings					1,435,970					1,435,970	1,257,632	1,127,380
Total InterDigital, Inc. shareholders’ equity					936,729					936,729	863,808	746,323
Noncontrolling interest					1,284					1,284	9,340	8,045
Total equity					$ 938,013					$ 938,013	$ 873,148	$ 754,368