Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Non-Controlling Interest
Beginning balance (in shares) at Dec. 31, 2016		70,318				(36,020)
Beginning balance at Dec. 31, 2016	$ 754,368	$ 703	$ 683,549	$ 1,127,380	$ (514)	$ (1,064,795)	$ 8,045
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to InterDigital, Inc.	176,220			176,220
Proceeds from and increases in noncontrolling interests	6,801						6,801
Net (loss) income attributable to noncontrolling interest	(5,506)						(5,506)
Net change in unrealized gain (loss) on short-term investments	(1,569)				(1,569)
Dividends declared	(45,122)		846	(45,968)
Exercise of common stock options (in shares)		9
Exercise of Common Stock options	382	$ 1	381
Issuance of common stock, net (in shares)		422
Issuance of Common Stock, net	(22,795)	$ 3	(22,798)
Amortization of unearned compensation	18,062		18,062
Repurchase of common stock (in shares)						107
Repurchase of Common Stock	(7,693)					$ (7,693)
Ending balance (in shares) at Dec. 31, 2017		70,749				(36,127)
Ending balance at Dec. 31, 2017	873,148	$ 707	680,040	1,257,632	(2,083)	$ (1,072,488)	9,340
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to InterDigital, Inc.	65,031			65,031
Net (loss) income attributable to noncontrolling interest	(5,556)						(5,556)
Net change in unrealized gain (loss) on short-term investments	61				61
Dividends declared	(47,922)		472	(48,394)
Exercise of common stock options (in shares)		153
Exercise of Common Stock options	6,723	$ 2	6,721
Issuance of common stock, net (in shares)		232
Issuance of Common Stock, net	(8,808)	$ 2	(8,810)
Amortization of unearned compensation	7,089		7,089
Repurchase of common stock (in shares)						1,478
Repurchase of Common Stock	(110,505)					$ (110,505)
Distribution preference	(2,500)						(2,500)
Ending balance (in shares) at Dec. 31, 2018		71,134				(37,605)
Ending balance at Dec. 31, 2018	938,013	$ 711	685,512	1,435,970	(2,471)	$ (1,182,993)	1,284
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to InterDigital, Inc.	20,928			20,928
Proceeds from and increases in noncontrolling interests	29,417						29,417
Net (loss) income attributable to noncontrolling interest	(5,977)						(5,977)
Net change in unrealized gain (loss) on short-term investments	2,397				2,397
Dividends declared	$ (43,718)		401	(44,119)
Exercise of common stock options (in shares)	0
Exercise of Common Stock options	$ 2		2
Issuance of common stock, net (in shares)		134
Issuance of Common Stock, net	(4,367)	$ 1	(4,368)
Amortization of unearned compensation	7,603		7,603
Repurchase of common stock (in shares)						2,962
Repurchase of Common Stock	(196,269)					$ (196,269)
Equity component of debt, net of tax	56,917		56,917
Net convertible note hedge transactions, net of tax	(49,740)		(49,740)
Net warrant transactions	43,416		43,416
Deferred financing costs allocated to equity, net of tax	(1,692)		(1,692)
Reacquisition of equity component of debt due to prepayment, net of tax	(10,649)		(10,649)
Ending balance (in shares) at Dec. 31, 2019		71,268				(40,567)
Ending balance at Dec. 31, 2019	$ 786,281	$ 712	$ 727,402	$ 1,412,779	$ (74)	$ (1,379,262)	$ 24,724