2. Summary of Significant Accounting Policies (Details - Basic and Diluted Loss Per Share) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net income (loss) attributable to Acacia Research Corporation	$ 80,239	$ 38,348	$ 6,148	$ (11,291)	$ 634	$ (7,608)	$ (5,757)	$ (4,384)	$ 113,444	$ (17,115)
Dividend on Series A redeemable convertible preferred stock									(1,381)	0
Accretion of Series A redeemable convertible preferred stock									(2,835)	(307)
Undistributed earnings allocated to participating securities									(18,898)	0
Net income (loss) attributable to common stockholders - basic	65,180	30,529	4,201	(12,185)	327	(7,608)	(5,757)	(4,384)	90,330	(17,422)
Add: Accretion of Series A redeemable convertible preferred stock									0	307
Less: Change in fair value of Series A redeemable convertible preferred stock embedded derivative									0	(3,258)
Less: Change in fair value of Series A warrants									(1,348)	0
Less: Change in fair value of dilutive Series B warrants									(5,557)	0
Add: Interest expense associated with Starboard Notes, net of tax									1,889	0
Add: Undistributed earnings allocated to participating securities									18,898	0
Reallocation of undistributed earnings to participating securities									(15,740)	0
Net income (loss) attributable to common stockholders - diluted	$ 65,352	$ 29,204	$ 4,201	$ (12,185)	$ (2,624)	$ (7,608)	$ (5,757)	$ (4,384)	$ 88,471	$ (20,373)
Denominator:
Weighted-average shares used in computing net income (loss) per share attributable to common stockholders - basic	48,508,903	48,467,885	48,457,620	49,875,396	49,875,750	49,828,361	49,696,016	49,655,881	48,840,829	49,764,002
Weighted-average shares used in computing net income (loss) per share attributable to common stockholders - diluted	49,244,141	90,624,702	49,033,824	49,875,396	54,406,835	49,828,361	49,696,016	49,655,881	57,435,128	50,896,773
Basic net income (loss) per common share	$ 1.34	$ 0.63	$ 0.09	$ 0.24	$ 0.01	$ 0.15	$ 0.12	$ 0.09	$ 1.85	$ (0.35)
Diluted net income (loss) per common share	$ 1.33	$ 0.32	$ 0.09	$ 0.24	$ 0.05	$ 0.15	$ 0.12	$ 0.09	$ 1.54	$ (0.40)
Series A Preferred Stock [Member]
Denominator:
Potentially dilutive common shares									0	1,132,771
Restricted Stock Units [Member]
Denominator:
Potentially dilutive common shares									637,044	0
Employee Stock Options [Member]
Denominator:
Potentially dilutive common shares									2,952	0
Series A Warrants [Member]
Denominator:
Potentially dilutive common shares									77,592	0
Series B Warrants [Member]
Denominator:
Potentially dilutive common shares									7,876,712	0