Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Treasury Stock	Additional Paid-In Capital	Accumulated Comprehensive Income / Loss	Accumulated Deficit	Noncontrolling Interest	Total
Beginning balance, shares at Dec. 31, 2017	50,639,926
Beginning balance, value at Dec. 31, 2017	$ 51	$ (34,640)	$ 648,996	$ (88)	$ (320,018)	$ 1,358	$ 295,659
Net loss attributable to Acacia Research Corporation					(93,660)		(93,660)
Cumulative effect of new accounting principle					2,506	307	2,813
Stock options exercised, shares	82,615
Stock options exercised, value			257				257
Compensation expense for share-based awards, net of forfeitures, shares	166,998
Compensation expense for share-based awards, net of forfeitures, value	$ 1		1,790				1,791
Repurchase of restricted common stock, shares	(59,800)
Repurchase of restricted common stock, value			(229)				(229)
Repurchase of common stock, shares	(1,190,420)
Repurchase of common stock, value	$ (2)	(4,632)					(4,634)
Net income (loss) attributable to noncontrolling interests in subsidiaries						179	179
Unrealized loss on foreign currency translation				(109)			(109)
Unrealized gain on short-term investments				75			75
Ending balance, shares at Sep. 30, 2018	49,639,319
Ending balance, value at Sep. 30, 2018	$ 50	(39,272)	650,814	(122)	(411,172)	1,844	202,142
Beginning balance, shares at Jun. 30, 2018	49,495,064
Beginning balance, value at Jun. 30, 2018	$ 49	(39,272)	650,265	(202)	(377,977)	1,513	234,376
Net loss attributable to Acacia Research Corporation					(33,195)		(33,195)
Stock options exercised, shares	66,115
Stock options exercised, value			206				206
Compensation expense for share-based awards, net of forfeitures, shares	135,896
Compensation expense for share-based awards, net of forfeitures, value	$ 1		565				566
Repurchase of restricted common stock, shares	(57,756)
Repurchase of restricted common stock, value			(222)				(222)
Net income (loss) attributable to noncontrolling interests in subsidiaries						331	331
Unrealized loss on foreign currency translation				(5)			(5)
Unrealized gain on short-term investments				85			85
Ending balance, shares at Sep. 30, 2018	49,639,319
Ending balance, value at Sep. 30, 2018	$ 50	(39,272)	650,814	(122)	(411,172)	1,844	202,142
Beginning balance, shares at Dec. 31, 2018	49,639,319
Beginning balance, value at Dec. 31, 2018	$ 50	(39,272)	651,156	0	(422,541)	1,847	191,240
Net loss attributable to Acacia Research Corporation					(17,749)		(17,749)
Stock options exercised, shares	25,136
Stock options exercised, value			79				79
Compensation expense for share-based awards, net of forfeitures, shares	678,850
Compensation expense for share-based awards, net of forfeitures, value			753				753
Net income (loss) attributable to noncontrolling interests in subsidiaries						(14)	(14)
Ending balance, shares at Sep. 30, 2019	50,343,305
Ending balance, value at Sep. 30, 2019	$ 50	(39,272)	651,988	0	(440,290)	1,833	174,309
Beginning balance, shares at Jun. 30, 2019	50,132,871
Beginning balance, value at Jun. 30, 2019	$ 50	(39,272)	651,688	0	(432,682)	1,833	181,617
Net loss attributable to Acacia Research Corporation					(7,608)		(7,608)
Compensation expense for share-based awards, net of forfeitures, shares	210,434
Compensation expense for share-based awards, net of forfeitures, value			300				300
Net income (loss) attributable to noncontrolling interests in subsidiaries							0
Ending balance, shares at Sep. 30, 2019	50,343,305
Ending balance, value at Sep. 30, 2019	$ 50	$ (39,272)	$ 651,988	$ 0	$ (440,290)	$ 1,833	$ 174,309