Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 21,902	$ 835	$ 40,832	$ 2,999
Unrealized gain (loss) on investments, net of tax	(362)	245	82	2,366
Comprehensive income	21,540	1,080	40,914	5,365
Comprehensive loss attributable to noncontrolling interest	(1,882)	(1,399)	(5,319)	(4,175)
Total comprehensive income attributable to InterDigital, Inc.	$ 23,422	$ 2,479	$ 46,233	$ 9,540