3. INCOME (LOSS) PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net income (loss) attributable to Acacia Research Corporation	$ 6,148	$ (5,757)	$ (5,143)	$ (10,141)
Dividend on Series A redeemable convertible preferred stock	(388)	0	(651)	0
Accretion of Series A redeemable convertible preferred stock	(680)	0	(1,311)	0
Undistributed earnings allocated to participating securities	(879)	0	0	0
Net income (loss) attributable to common stockholders - basic and diluted	$ 4,201	$ (5,757)	$ (7,105)	$ (10,141)
Denominator:
Weighted-average shares used in computing net income (loss) per share attributable to common stockholders - basic	48,457,620	49,696,016	49,166,508	49,676,059
Restricted stock units	576,204	0	0	0
Weighted-average shares used in computing net income (loss) per share attributable to common stockholders - diluted	49,033,824	49,696,016	49,166,508	49,676,059
Basic net income (loss) per common share	$ 0.09	$ (0.12)	$ (0.14)	$ (0.20)
Diluted net income (loss) per common share	$ 0.09	$ (0.12)	$ (0.14)	$ (0.20)
Antidilutive shares	105,476,583	1,766,191	107,321,016	1,766,191
Equity Based Incentive Awards [Member]
Denominator:
Antidilutive shares	476,583	1,766,191	2,321,016	1,766,191
Series A Warrants [Member]
Denominator:
Antidilutive shares	5,000,000	0	5,000,000	0
Series B Warrants [Member]
Denominator:
Antidilutive shares	100,000,000	0	100,000,000	0