Quarterly Financial Data (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
QUARTERLY FINANCIAL DATA (unaudited) [Abstract]
Revenues	$ 66,264	$ 34,939	$ 50,484	$ 99,040	$ 20,795	$ 50,585	$ 39,746	$ 61,130	$ 250,727	$ 172,256	$ 131,829
Inventor royalties	3,829	5,032	9,573	7,594	6,458	15,592	8,588	13,089	26,028	43,727	25,292
Contingent legal fees	5,463	8,833	6,607	3,748	5,547	12,328	13,039	9,367	24,651	40,281	19,906
Litigation and licensing expenses - patents	6,969	5,973	5,268	3,381	2,205	3,501	3,761	3,538	21,591	13,005	13,891
Amortization of patents	18,088	10,412	5,393	5,126	1,427	1,946	2,600	3,772	39,019	9,745	6,931
Verdict insurance proceeds	0	0	0	0	0	(12,451)	0	0	0	(12,451)	0
Verdict insurance proceeds related costs	0	0	0	0	0	7,661	0	0	0	7,661	0
Marketing, general and administrative expenses (including non-cash stock compensation expense)	(16,535)	(11,914)	(11,903)	(13,731)	(8,662)	(8,748)	(8,302)	(9,981)	(54,083)	(35,693)	(25,067)
Research, consulting and other expenses - business development	721	1,139	1,967	1,116	1,445	850	1,335	708	4,943	4,338	2,121
Total operating costs and expenses	51,605	43,303	40,711	34,696	25,744	38,175	37,625	40,455	170,315	141,999	93,208
Operating income (loss)	14,659	(8,364)	9,773	64,344	(4,949)	12,410	2,121	20,675	80,412	30,257	38,621
Total other income	820	(41)	102	56	18	25	24	29
Income (loss) from operations before provision for income taxes	15,479	(8,405)	9,875	64,400	(4,931)	12,435	2,145	20,704	81,349	30,353	38,756
(Provision) benefit for income taxes	5,757	(1,938)	3,494	14,747	(635)	1,889	306	7,148	22,060	8,708	1,740
Net income (loss) including noncontrolling interests in operating subsidiaries	9,722	(6,467)	6,381	49,653	(4,296)	10,546	1,839	13,556	59,289	21,645	37,016
Net (income) loss attributable to noncontrolling interests	101	(152)	(60)	275	107	257	300	(1,203)	164	(539)	(2,965)
Net income (loss) attributable to Acacia Research Corporation	$ 9,823	$ (6,619)	$ 6,321	$ 49,928	$ (4,189)	$ 10,803	$ 2,139	$ 12,353	$ 59,453	$ 21,106	$ 34,051
Earnings Per Share, Basic	$ 0.20	$ (0.14)	$ 0.13	$ 1.13	$ (0.10)	$ 0.26	$ 0.05	$ 0.35	$ 1.26	$ 0.53	$ 1.05
Earnings Per Share, Diluted	$ 0.20	$ (0.14)	$ 0.13	$ 1.09	$ (0.10)	$ 0.25	$ 0.05	$ 0.34	$ 1.24	$ 0.51	$ 0.97
Weighted-average common shares outstanding - basic	48,335,865	48,332,878	47,944,193	44,367,499	41,418,470	41,292,819	40,994,082	35,182,811	47,251,061	39,743,433	32,306,322
Weighted-average common shares outstanding - diluted	48,797,304	48,332,878	48,938,766	45,771,228	41,418,470	42,857,880	42,453,782	36,448,005	48,060,647	41,258,297	35,081,611