INCOME/LOSS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net income (loss) attributable to Acacia Research Corporation	$ 89,604	$ 38,348	$ (55,507)	$ 33,205
Dividend on Series A redeemable convertible preferred stock	(262)	(467)	(785)	(1,118)
Accretion of Series A redeemable convertible preferred stock	(991)	(733)	(2,762)	(2,045)
Undistributed earnings allocated to participating securities	(15,367)	(6,619)	0	(5,204)
Net income (loss) attributable to common stockholders - Basic	72,984	30,529	(59,054)	24,838
Add: Dividend on Series A redeemable convertible preferred stock	0	467	0	0
Add: Accretion of Series A redeemable convertible preferred stock	0	733	0	0
Less: Change in fair value of Series A redeemable convertible preferred stock embedded derivative	0	(3,831)	0	0
Less: Change in fair value of Series A warrants	63	(1,348)	0	(1,348)
Less: Change in fair value of dilutive Series B warrants	(902)	(5,557)		(5,557)
Add: Interest expense associated with Starboard Notes, net of tax	1,536	1,889		1,889
Add: Undistributed earnings allocated to participating securities	15,367	6,619	0	5,204
Reallocation of undistributed earnings to participating securities	(8,877)	(296)	0	(3,645)
Net income (loss) attributable to common stockholders - Diluted	$ 80,171	$ 29,205	$ (59,054)	$ 21,381
Denominator:
Weighted-average shares used in computing net income (loss) per share attributable to common stockholders - Basic	48,949,504	48,467,885	48,759,873	48,949,706
Potentially dilutive common shares:
Potentially dilutive common shares	93,081,502	90,624,702	48,759,873	60,153,773
Weighted-average shares used in computing net income (loss) per share attributable to common stockholders - Diluted	93,081,502	90,624,702	48,759,873	60,153,773
Basic net income (loss) per common share	$ 1.49	$ 0.63	$ (1.21)	$ 0.51
Diluted net income (loss) per common share	$ 0.86	$ 0.32	$ (1.21)	$ 0.36
Anti-dilutive potential common shares excluded from the computation of diluted net income (loss) per common share:
Antidilutive shares	398,168	68,684,463	107,230,624	68,803,234
Equity Based Incentive Awards [Member]
Anti-dilutive potential common shares excluded from the computation of diluted net income (loss) per common share:
Antidilutive shares	398,168	191,312	2,230,624	310,083
Series A Warrants [Member]
Anti-dilutive potential common shares excluded from the computation of diluted net income (loss) per common share:
Antidilutive shares	0	0	5,000,000	0
Series B Warrants [Member]
Anti-dilutive potential common shares excluded from the computation of diluted net income (loss) per common share:
Antidilutive shares	0	68,493,151	100,000,000	68,493,151
Series A Preferred Stock [Member]
Potentially dilutive common shares:
Potentially dilutive common shares	0	9,589,041	0	0
Restricted Stock Units [Member]
Potentially dilutive common shares:
Potentially dilutive common shares	798,356	728,936	0	598,328
Employee Stock Options [Member]
Potentially dilutive common shares:
Potentially dilutive common shares	35,815	21,624	0	0
Series A Warrants [Member]
Potentially dilutive common shares:
Potentially dilutive common shares	2,019,724	310,367	0	103,456
Series B Warrants [Member]
Potentially dilutive common shares:
Potentially dilutive common shares	41,278,103	31,506,849	0	10,502,283