Quarterly Financial Data (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
QUARTERLY FINANCIAL DATA (unaudited) [Abstract]
Revenues	$ 31,030	$ 37,192	$ 50,076	$ 12,578	$ 15,065	$ 15,520	$ 23,110	$ 76,861
Inventor royalties	4,358	4,667	10,694	951	3,280	2,353	5,610	18,481	20,670	29,724	26,028
Contingent legal fees	7,296	7,663	7,077	1,527	3,181	2,547	4,024	15,032	23,563	24,784	24,651
Litigation and licensing expenses - patents	8,208	9,592	10,820	8,994	8,899	10,870	9,918	9,648	37,614	39,335	21,591
Amortization of patents	13,727	13,511	15,532	14,472	16,735	12,615	12,578	11,730	57,242	53,658	39,019
Marketing, general and administrative expenses (including non-cash stock compensation expense)	(12,044)	(11,636)	(13,181)	(11,693)	(13,988)	(18,235)	(13,184)	(13,844)	(48,554)	(59,229)	(54,083)
Research, consulting and other expenses - business development	637	1,208	1,003	992	742	730	726	1,031	3,840	3,251	4,943
Other	0	1,548	0	0	0	3,506	0	0	1,548	3,506	0
Total operating costs and expenses	46,270	49,825	58,307	38,629	46,825	50,856	46,040	69,766	193,031	213,487	170,315
Operating income (loss)	(15,240)	(12,633)	(8,231)	(26,051)	(31,760)	(35,336)	(22,930)	7,095	(62,155)	(82,931)	80,412
Total other income (expense)	(451)	(57)	(196)	109	161	280	400	1,290	(595)	2,131	937
Income (loss) from operations before (provision for) benefit from income taxes	(15,691)	(12,690)	(8,427)	(25,942)	(31,599)	(35,056)	(22,530)	8,385	(62,750)	(80,800)	81,349
(Provision) benefit for income taxes	(450)	(145)	(4,689)	1,372	(3,390)	19,570	9,050	(3,272)	(3,912)	21,958	(22,060)
Net income (loss) including noncontrolling interests in operating subsidiaries	(16,141)	(12,835)	(13,116)	(24,570)	(34,989)	(15,486)	(13,480)	5,113	(66,662)	(58,842)	59,289
Net (income) loss attributable to noncontrolling interests in operating subsidiaries	103	(420)	(167)	(149)	(1,656)	225	(977)	0	(633)	(2,408)	(164)
Net income (loss) attributable to Acacia Research Corporation	$ (16,244)	$ (12,415)	$ (12,949)	$ (24,421)	$ (33,333)	$ (15,711)	$ (12,503)	$ 5,113	$ (66,029)	$ (56,434)	$ 59,453
Basic income (loss) per share - As Adjusted(1)	$ (0.34)	$ (0.26)	$ (0.27)	$ (0.51)	$ (0.69)	$ (0.33)	$ (0.26)	$ 0.10	$ (1.37)	$ (1.18)	$ 1.22
Diluted income (loss) per share - As Adjusted(1)	$ (0.34)	$ (0.26)	$ (0.27)	$ (0.51)	$ (0.69)	$ (0.33)	$ (0.26)	$ 0.10	$ (1.37)	$ (1.18)	$ 1.21
Weighted-average number of shares outstanding, basic - As Adjusted(1)	48,944,914	48,806,334	48,543,334	48,329,375	48,415,684	48,330,149	48,008,998	47,859,774	48,658,088	48,155,832	47,251,061
Weighted-average number of shares outstanding, diluted - As Adjusted(1)	48,944,914	48,806,334	48,543,334	48,329,375	48,415,684	48,330,149	48,008,998	48,104,242	48,658,088	48,155,832	47,584,120
Earnings (loss) per share, basic, as previously reported							$ (0.26)	$ 0.11
Earnings (loss) per share, diluted as previously reported							$ (0.26)	$ 0.11
Weighted average number of shares, basic, as previously reported							48,008,998	47,859,774
Weighted average number of shares, diluted, as previously reported							48,008,998	48,354,444