Cover - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Mar. 25, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-37721
Entity Registrant Name	ACACIA RESEARCH CORP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	95-4405754
Entity Address, Address Line One	767 Third Avenue,
Entity Address, Address Line Two	6th Floor
Entity Address, City or Town	New York,
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10017
City Area Code	949
Local Phone Number	480-8300
Title of 12(b) Security	Common Stock
Trading Symbol	ACTG
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
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
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 330,094
Entity Common Stock, Shares Outstanding		46,474,683
Documents Incorporated by Reference	In accordance with General Instruction G(3) to Form 10-K, portions of the registrant’s Definitive Proxy Statement on Schedule 14A for its Annual Meeting of Stockholders to be filed with the Commission within 120 days after the close of the fiscal year covered by this Annual Report on Form 10-K are incorporated by reference into Part III of this Annual Report on Form 10-K. Only those portions of the proxy statement that are specifically incorporated by reference herein shall constitute a part of this Annual Report on Form 10-K.
Amendment Flag	false
Entity Central Index Key	0000934549
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY