UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Revenues	$ 1,582	$ 19,466	$ 24,785	$ 25,399
Patent portfolio operations:
Inventor royalties	280	5,772	823	6,843
Contingent legal fees	285	6,609	5,735	6,855
Litigation and licensing expenses - patents	782	1,001	4,881	3,497
Amortization of patents	2,612	1,174	7,086	3,522
Other patent portfolio income	0	0	0	(308)
Patent portfolio expenses	3,959	14,556	18,525	20,409
Net patent portfolio (loss) income	(2,377)	4,910	6,260	4,990
General and administrative expenses	10,345	7,692	23,014	18,089
Operating loss	(12,722)	(2,782)	(16,754)	(13,099)
Other income (expense):
Change in fair value of investment, net	0	(3,081)	(2,752)	3,704
Gain (loss) on sale of investment	0	0	3,591	(2,762)
Change in fair value of the Series A and B warrants and embedded derivatives	619	20,672	(203,866)	(46,612)
Gain on sale of prepaid investment and derivative	0	2,845	0	2,845
Change in fair value of equity securities	66,502	20,488	115,509	99,449
Gain (loss) on sale of equity securities	37,688	2,737	53,124	(4,272)
Earnings on equity investment in joint venture	0	0	2,737	0
Loss on foreign currency exchange	(17)	(48)	(193)	(4,938)
Interest expense on Senior Secured Notes	(2,531)	(2,410)	(5,601)	(3,178)
Interest income and other	76	10	135	811
Total other income (expense)	102,337	41,213	(37,316)	45,047
Income (loss) before income taxes	89,615	38,431	(54,070)	31,948
Income tax (expense) benefit	(11)	(83)	(531)	1,257
Net income (loss) including noncontrolling interests in subsidiaries	89,604	38,348	(54,601)	33,205
Net income attributable to noncontrolling interests in subsidiaries	0	0	(906)	0
Net income (loss) attributable to Acacia Research Corporation	$ 89,604	$ 38,348	$ (55,507)	$ 33,205
Net income (loss) attributable to common stockholders - Basic	$ 72,984	$ 30,529	$ (59,054)	$ 24,838
Basic net income (loss) per common share	$ 1.49	$ 0.63	$ (1.21)	$ 0.51
Weighted average number of shares outstanding - Basic	48,949,504	48,467,885	48,759,873	48,949,706
Net income (loss) attributable to common stockholders - Diluted	$ 80,171	$ 29,204	$ (59,054)	$ 21,380
Diluted net income (loss) per common share	$ 0.86	$ 0.32	$ (1.21)	$ 0.36
Weighted average number of shares outstanding - Diluted	93,081,502	90,624,702	48,759,873	60,153,773