Summary of Significant Accounting Policies Earnings per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Net income (loss) attributable to Acacia Research Corporation	$ (110,203)	$ 158,465	$ (14,252)	$ (11,830)	$ (10,611)	$ 7,082	$ (40,573)	$ (9,965)	$ 22,180	$ (54,067)	$ (160,036)
Undistributed Earnings (Loss) Allocated to Participating Securities, Basic									33	0	0
Payments of Dividends									0	0	(25,434)
Dividends attributable to common stockholders under the two class method									0	0	24,740
Net Loss Available to Common Stockholders, Basic and Diluted									$ 22,147	$ (54,067)	$ (160,730)
Weighted Average Number of Shares Outstanding, Basic									50,495,119	50,075,847	49,505,817
Weighted Average Number Diluted Shares Outstanding Adjustment									196,893	0	0
Weighted Average Number of Shares Outstanding, Diluted	50,590,460	50,599,974	50,499,948	50,333,056	50,237,784	50,618,757	50,015,869	49,925,550	50,692,012	50,075,847	49,505,817
Earnings Per Share, Basic and Diluted	$ (2.18)	$ 3.13	$ (0.28)	$ (0.24)	$ (0.21)	$ 0.14	$ (0.81)	$ (0.20)	$ 0.44	$ (1.08)	$ (3.25)
Anti-dilutive equity-based incentive awards excluded from the computation of diluted income (loss) per share									4,425,187	3,682,532	71,468