Cover - USD ($)	12 Months Ended
	Dec. 31, 2020	Mar. 24, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Entity File Number	001-37721
Entity Registrant Name	ACACIA RESEARCH CORP
Entity Central Index Key	0000934549
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		49,279,453
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
State of Incorporation	DE
Entity Shell Company	false
Entity Public Float			$ 199,263,000
Well Known Seasoned Issuer	No
Entity Voluntary Filer	No