Revenue Recognition - Schedule of Impact of Adoption of ASC 606 (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
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ 102,161	$ 72,523	$ 75,609	$ 68,631	$ 75,326	$ 75,079	$ 69,555	$ 87,444	$ 318,924	$ 307,404	$ 532,938
Operating expenses									281,089	244,809	231,443
Income from operations									37,835	62,595	301,495
Interest expense									(40,955)	(35,956)	(17,845)
OTHER INCOME (EXPENSE), NET									29,062	5,419	8,740
Income before income taxes									25,942	32,058	292,390
INCOME TAX BENEFIT (PROVISION)									(10,991)	27,417	(121,676)
NET INCOME									14,951	59,475	170,714
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
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										$ 74,709
Operating expenses										0
Income from operations										74,709
Interest expense										16,655
OTHER INCOME (EXPENSE), NET										0
Income before income taxes										91,364
INCOME TAX BENEFIT (PROVISION)										(6,686)
NET INCOME										84,678
Net loss attributable to noncontrolling interest										0
Net income attributable to InterDigital, Inc.										$ 84,678
Net income per share — basic (in usd per share)										$ 2.45
Net income per share — diluted (in usd per share)										$ 2.40
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										$ 382,113	$ 532,938
Operating expenses										244,809	231,443
Income from operations										137,304	301,495
Interest expense										(19,301)	(17,845)
OTHER INCOME (EXPENSE), NET										5,419	8,740
Income before income taxes										123,422	292,390
INCOME TAX BENEFIT (PROVISION)										20,731	(121,676)
NET INCOME										144,153	170,714
Net loss attributable to noncontrolling interest										(5,556)	(5,506)
Net income attributable to InterDigital, Inc.										$ 149,709	$ 176,220
Net income per share — basic (in usd per share)										$ 4.34	$ 5.09
Net income per share — diluted (in usd per share)										$ 4.24	$ 4.93
Total Patent Royalties
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues									$ 307,431	$ 302,060
Total Patent Royalties | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										69,802
Total Patent Royalties | Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										371,862	$ 512,358
Variable Patent Royalty Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues									30,428	36,384
Variable Patent Royalty Revenue | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										461
Variable Patent Royalty Revenue | Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										36,845	47,840
Fixed-Fee Royalty Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues									257,221	239,347
Fixed-Fee Royalty Revenue | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										79,341
Fixed-Fee Royalty Revenue | Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										318,688	301,628
Current Patent Royalties
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues									287,649	275,731
Current Patent Royalties | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										79,802
Current Patent Royalties | Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										355,533	349,468
Non-Current Patent Royalties
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues									19,782	26,329
Non-Current Patent Royalties | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										(10,000)
Non-Current Patent Royalties | Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										16,329	162,890
Patent Sales
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues									975	750
Patent Sales | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										0
Patent Sales | Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										750	0
Current Technology Solutions
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues									$ 10,518	4,594
Current Technology Solutions | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										4,907
Current Technology Solutions | Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues										$ 9,501	$ 20,580