UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF SERIES A REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Series A Redeemable Convertible Preferred Stock [Member]	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Noncontrolling Interest [Member]	Total
Beginning balance, value at Dec. 31, 2019	$ 8,089	$ 50	$ (39,272)	$ 652,003	$ (439,656)	$ 1,833	$ 174,958
Balance at beginning, shares at Dec. 31, 2019	350,000	50,370,987
Net income attributable to Acacia Research Corporation					33,205		33,205
Accretion of Series A Redeemable Convertible Preferred Stock to redemption value	2,045			(2,045)			(2,045)
Dividend on Series A Redeemable Convertible Preferred Stock				(1,119)			(1,119)
Stock options exercised				48			48
Stock options exercised, Shares		13,333
Issuance of common stock for vesting of restricted stock units
Issuance of common stock for vesting of restricted stock units, shares		14,354
Issuance of common stock for unvested restricted stock awards, net of forfeitures
Issuance of common stock for unvested restricted stock awards, net of forfeitures, shares		565,316
Compensation expense for share-based awards				1,243			1,243
Repurchase of common stock		$ (1)	(3,998)				(3,999)
Repurchase of common stock, Shares		(1,684,537)
Ending balance, value at Sep. 30, 2020	$ 10,134	$ 49	(43,270)	650,130	(406,451)	1,833	202,291
Balance at ending, shares at Sep. 30, 2020	350,000	49,279,453
Beginning balance, value at Jun. 30, 2020	$ 9,400	$ 49	(43,270)	650,843	(444,799)	1,833	164,656
Balance at beginning, shares at Jun. 30, 2020	350,000	49,306,137
Net income attributable to Acacia Research Corporation					38,348		38,348
Accretion of Series A Redeemable Convertible Preferred Stock to redemption value	734			(734)			(734)
Dividend on Series A Redeemable Convertible Preferred Stock				(467)			(467)
Issuance of common stock for unvested restricted stock awards, net of forfeitures
Issuance of common stock for unvested restricted stock awards, net of forfeitures, shares		(26,684)
Compensation expense for share-based awards				488			488
Ending balance, value at Sep. 30, 2020	$ 10,134	$ 49	(43,270)	650,130	(406,451)	1,833	202,291
Balance at ending, shares at Sep. 30, 2020	350,000	49,279,453
Beginning balance, value at Dec. 31, 2020	$ 10,924	$ 49	(43,270)	651,416	(326,708)	11,042	292,529
Balance at beginning, shares at Dec. 31, 2020	350,000	49,279,453
Net income attributable to Acacia Research Corporation							(54,601)
Net (loss) income including noncontrolling interests in subsidiaries					(55,507)	906	(54,601)
Accretion of Series A Redeemable Convertible Preferred Stock to redemption value	2,762			(2,762)			(2,762)
Dividend on Series A Redeemable Convertible Preferred Stock				(785)			(785)
Stock options exercised		$ 1		201			202
Stock options exercised, Shares		60,000
Issuance of common stock for vesting of restricted stock units
Issuance of common stock for vesting of restricted stock units, shares		28,834
Issuance of common stock for unvested restricted stock awards, net of forfeitures
Issuance of common stock for unvested restricted stock awards, net of forfeitures, shares		223,565
Compensation expense for share-based awards				1,279			1,279
Ending balance, value at Sep. 30, 2021	$ 13,686	$ 50	(43,270)	649,349	(382,215)	11,948	235,862
Balance at ending, shares at Sep. 30, 2021	350,000	49,591,852
Beginning balance, value at Jun. 30, 2021	$ 12,695	$ 50	(43,270)	650,194	(471,819)	11,948	147,103
Balance at beginning, shares at Jun. 30, 2021	350,000	49,616,602
Net income attributable to Acacia Research Corporation							89,604
Net (loss) income including noncontrolling interests in subsidiaries					89,604		89,604
Accretion of Series A Redeemable Convertible Preferred Stock to redemption value	991			(991)			(991)
Dividend on Series A Redeemable Convertible Preferred Stock				(262)			(262)
Stock options exercised				108			108
Stock options exercised, Shares		30,000
Issuance of common stock for unvested restricted stock awards, net of forfeitures
Issuance of common stock for unvested restricted stock awards, net of forfeitures, shares		(54,750)
Compensation expense for share-based awards				300			300
Ending balance, value at Sep. 30, 2021	$ 13,686	$ 50	$ (43,270)	$ 649,349	$ (382,215)	$ 11,948	$ 235,862
Balance at ending, shares at Sep. 30, 2021	350,000	49,591,852