Acquisitions Pro Forma Information (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Jun. 30, 2011	Jun. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Business Acquisition [Line Items]
Revenues	$ 34,939	$ 50,585			$ 184,463
Total operating costs and expenses	43,303	42,364			119,348	129,234
Operating income (loss)	(8,364)	8,221			65,115	22,227
Interest and investment income	(41)	25			117	78
Income (loss) from operations before provision for income taxes	(8,405)	8,246			65,232	22,305
Provision for income taxes	1,938	(1,889)			(16,303)	(9,343)
Net income (loss) including noncontrolling interests in operating subsidiaries	(6,467)	6,357			48,929	12,962
Net (income) loss attributable to noncontrolling interests in operating subsidiaries	(152)	257			63	(646)
Net income (loss) attributable to Acacia Research Corporation	$ (6,619)	$ 6,614			$ 48,992	$ 12,316
Pro forma income (loss) per common share attributable to Acacia Research Corporation: Basic earnings (loss) per share	$ (0.14)		$ 0.16	$ 0.31	$ 1.04
Pro forma income (loss) per common share attributable to Acacia Research Corporation: Diluted earnings (loss) per share	$ (0.14)		$ 0.15	$ 0.30	$ 1.03
Weighted average number of shares outstanding, basic	48,332,878		41,292,819	39,178,952	46,886,820
Weighted average number of shares outstanding, diluted	48,332,878		42,857,880	40,733,813	47,795,819