The Company	3 Months Ended
Dec. 31, 2011
The Company [Abstract]
The Company	Unless otherwise noted, (1) the term "Arrowhead" refers to Arrowhead Research Corporation, a Delaware corporation, (2) the terms the "Company," "we," "us," and "our," refer to the ongoing business operations of Arrowhead and its Subsidiaries, whether conducted through Arrowhead or a subsidiary of Arrowhead, (3) the term "Subsidiaries" refers collectively to Arrowhead Madison Inc. ("Madison") , Calando Pharmaceuticals, Inc. ("Calando"), Ablaris Therapeutics, Inc. ("Ablaris"), Agonn Systems, Inc. ("Agonn"), and Tego Biosciences Corporation ("Tego") as well as our former subsidiary, Unidym, Inc. ("Unidym"), which was divested in January 2011, (4) the term "Minority Investments" refers collectively to Nanotope, Inc. ("Nanotope") and Leonardo Biosystems, Inc. ("Leonardo") in which the company holds a less than majority ownership position, and (5) the term "Common Stock" refers to Arrowhead's Common Stock and the term "stockholder(s)" refers to the holders of Arrowhead Common Stock.

Unless otherwise noted, (1) the term "Arrowhead" refers to Arrowhead Research Corporation, a Delaware corporation, (2) the terms the "Company," "we," "us," and "our," refer to the ongoing business operations of Arrowhead and its Subsidiaries, whether conducted through Arrowhead or a subsidiary of Arrowhead, (3) the term "Subsidiaries" refers collectively to Arrowhead Madison Inc. ("Madison") , Calando Pharmaceuticals, Inc. ("Calando"), Ablaris Therapeutics, Inc. ("Ablaris"), Agonn Systems, Inc. ("Agonn"), and Tego Biosciences Corporation ("Tego") as well as our former subsidiary, Unidym, Inc. ("Unidym"), which was divested in January 2011, (4) the term "Minority Investments" refers collectively to Nanotope, Inc. ("Nanotope") and Leonardo Biosystems, Inc. ("Leonardo") in which the company holds a less than majority ownership position, and (5) the term "Common Stock" refers to Arrowhead's Common Stock and the term "stockholder(s)" refers to the holders of Arrowhead Common Stock.