Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]	Noncontrolling Interests [Member]
Balance at Dec. 31, 2016	$ 267,443	$ 50	$ (34,640)	$ 642,453	$ (76)	$ (342,198)	$ 1,854
Common stock, shares outstanding at Dec. 31, 2016		50,476,042
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to Acacia Research Corporation	22,180					22,180
Stock Repurchased During Period, Shares		(8,669)
Stock options exercised, shares		207,863
Proceeds from Stock Options Exercised	745	$ 1		744
Stock options exercised, value	745
Stock issued during period, shares, share-based compensation, net of forfeitures		(35,310)
Non-cash stock compensation	8,885	$ 0
General and administrative expenses excluding share-based compensation	5,844			5,844
Net (income) loss attributable to noncontrolling interests in subsidiaries	(496)						(496)
Foreign Currency Transaction Gain (Loss), Unrealized	28				28
Unrealized Gain (Loss) on Investments	(40)				(40)
Payments for Repurchase of Common Stock	0
Repurchase of restricted common stock	(45)			45
Balance at Dec. 31, 2017	$ 295,659	$ 51	(34,640)	648,996	(88)	(320,018)	1,358
Common stock, shares outstanding at Dec. 31, 2017	50,639,926	50,639,926
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to Acacia Research Corporation	$ (105,029)					(105,029)
Treasury stock, shares acquired		(1,190,420)
Stock Repurchased During Period, Shares	1,190,420	(59,800)
Stock options exercised, shares	83,000	82,615
Proceeds from Stock Options Exercised	$ 257			257
Stock options exercised, value	257
Stock issued during period, shares, share-based compensation, net of forfeitures		166,998
Non-cash stock compensation	(317)	$ 1
General and administrative expenses excluding share-based compensation	2,133			2,132
Net (income) loss attributable to noncontrolling interests in subsidiaries	181						181
Foreign Currency Transaction Gain (Loss), Unrealized	88				88
Payments for Repurchase of Common Stock	(4,634)	2	4,632
Repurchase of restricted common stock	(229)			229
Balance at Dec. 31, 2018	$ 191,240	$ 50	$ (39,272)	$ 651,156	$ 0	(422,541)	1,847
Common stock, shares outstanding at Dec. 31, 2018	49,639,319	49,639,319
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 2,814					$ 2,506	$ 308
Treasury Stock, Common, Value	$ (4,634)