Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Revenues	$ 29,782	$ 11,246
Portfolio operations:
Inventor royalties	7,349	4,944
Contingent legal fees	7,419	591
Litigation and licensing expenses - patents	5,683	7,803
Amortization of patents	4,681	3,194
Other portfolio expenses (income)	(308)	1,756
Total portfolio expenses	24,824	18,288
Net portfolio income (loss)	4,958	(7,042)
Acquisition of MalinJ1	24,476	16,376
Operating loss	(19,518)	(23,418)
Other income (expense):
Change in fair value of investment, net (Note 6)	5,474	9,899
Gain (loss) on sale of investment (Note 6)	8,187	(9,230)
Impairment of other investment	0	(8,195)
Gain on disposal of other investment	0	2,000
Change in fair value of the Series A and B warrants and embedded derivatives	(58,238)	4,518
Gain on sale of prepaid investment and derivative	2,845	0
Change in fair value of trading securities and equity securities	176,173	(145)
Gain on sale of trading securities	7,352	2,188
Loss on foreign currency exchange	(4,905)	(2)
Interest expense on Senior Secured Notes	(5,923)	0
Interest income and other	838	3,432
Total other income	131,803	4,465
Income (loss) before income taxes	112,285	(18,953)
Income tax benefit	1,159	1,824
Net income (loss) including noncontrolling interests in subsidiaries	113,444	(17,129)
Net loss attributable to noncontrolling interests in subsidiaries	0	14
Net income (loss) attributable to Acacia Research Corporation	113,444	(17,115)
Net income (loss) attributable to common stockholders - basic	$ 90,330	$ (17,422)
Basic net income (loss) per common share	$ 1.85	$ (0.35)
Weighted average number of shares outstanding - basic	48,840,829	49,764,002
Net income (loss) attributable to common stockholders - diluted	$ 88,471	$ (20,373)
Diluted net income (loss) per common share	$ 1.54	$ (0.40)
Weighted average number of shares outstanding - diluted	57,435,128	50,896,773