Consolidated Statement of Stockholders' Equity (USD $)	Total	Issued for cash at $0.01 per unit [Member]	Issued for cash at $10.00 per unit [Member]	Stock issuance cost charged to additional paid-in capital [Member]	Issued for marketable securities at $10.00 per unit [Member]	Issued for cash at $15.00 per unit [Member]	Issued in acquisition [Member]	Issued as a gift for $10.90 per share [Member]	Issued as stock issuance cost at $15.00 per unit [Member]	Exercised at $2.00 per share [Member]	Exercised at $10.00 per share [Member]	Exercised at $15.00 per share [Member]	Issued to purchase Insert Therapeutics share at $39.80 per share [Member]	Issued at $48.80 per share [Member]	Issued at $38.40 per share [Member]	Issued at $35.00 per share [Member]	Issued at $59.10 per share [Member]	Issued to purchase Calando Pharmaceuticals, Inc. at $51.70 per share [Member]	Issued at $57.80 per share, net [Member]	Issued for purchase of Carbon Nanotechnologies, Inc. at $37.70 per share [Member]	Issued at approximately $18.00 per share, net [Member]	Arrowhead's increase in proportionate share of Insert Therapeutics' equity [Member]	Issued at $27.20 per share to Rice University [Member]	Issued at $28.30 per share to purchase shares of Unidym, Inc. [Member]	Issued at $29.50 per share to purchase MASA Energy, LLC [Member]	Issued at $21.90 per share to Unidym for the acquisition of Nanoconduction [Member]	Issued at $21.80 per share [Member]	Issued at $5.50 per share to Unidym Stockholder in exchange for Unidym's shares [Member]	Issued at $5.20 per share to TEL Ventures in exchange for Unidym's shares [Member]	Arrowhead's increase in proportionate share of Calando's equity [Member]	Issued at $3.00 per share [Member]	Issued to Unidym stockholders in exchange for Unidym's shares [Member]	Issued at $6.30 per share [Member]	Issued at $13.12 per share [Member]	Issued to Calando stockholders in exchange for Calando's Shares [Member]	Issued at $3.80 per share [Member]	Issued at $3.70 per share [Member]	Issued at $4.00 per share [Member]	Issued at $6.23 per share [Member]	Issued at $5.11 per share [Member]	Issued at $2.76 per share [Member]	Preferred stock issued @ $1,000 per share [Member]	Issued @ $2.26 per share [Member]	Issued @ $4.49 per share [Member]	Common Stock [Member]	Common Stock [Member] Issued for cash at $0.01 per unit [Member]	Common Stock [Member] Issued for cash at $10.00 per unit [Member]	Common Stock [Member] Issued for marketable securities at $10.00 per unit [Member]	Common Stock [Member] Issued for cash at $15.00 per unit [Member]	Common Stock [Member] Issued in acquisition [Member]	Common Stock [Member] Issued as a gift for $10.90 per share [Member]	Common Stock [Member] Issued as stock issuance cost at $15.00 per unit [Member]	Common Stock [Member] Exercised at $2.00 per share [Member]	Common Stock [Member] Exercised at $10.00 per share [Member]	Common Stock [Member] Exercised at $15.00 per share [Member]	Common Stock [Member] Issued to purchase Insert Therapeutics share at $39.80 per share [Member]	Common Stock [Member] Issued at $48.80 per share [Member]	Common Stock [Member] Issued at $38.40 per share [Member]	Common Stock [Member] Issued at $35.00 per share [Member]	Common Stock [Member] Issued at $59.10 per share [Member]	Common Stock [Member] Issued to purchase Calando Pharmaceuticals, Inc. at $51.70 per share [Member]	Common Stock [Member] Issued at $57.80 per share, net [Member]	Common Stock [Member] Issued for purchase of Carbon Nanotechnologies, Inc. at $37.70 per share [Member]	Common Stock [Member] Issued at approximately $18.00 per share, net [Member]	Common Stock [Member] Issued at $27.20 per share to Rice University [Member]	Common Stock [Member] Issued at $28.30 per share to purchase shares of Unidym, Inc. [Member]	Common Stock [Member] Issued at $29.50 per share to purchase MASA Energy, LLC [Member]	Common Stock [Member] Issued at $21.90 per share to Unidym for the acquisition of Nanoconduction [Member]	Common Stock [Member] Issued at $21.80 per share [Member]	Common Stock [Member] Issued at $5.50 per share to Unidym Stockholder in exchange for Unidym's shares [Member]	Common Stock [Member] Issued at $5.20 per share to TEL Ventures in exchange for Unidym's shares [Member]	Common Stock [Member] Issued at $3.00 per share [Member]	Common Stock [Member] Issued to Unidym stockholders in exchange for Unidym's shares [Member]	Common Stock [Member] Issued at $6.30 per share [Member]	Common Stock [Member] Issued at $13.12 per share [Member]	Common Stock [Member] Issued to Calando stockholders in exchange for Calando's Shares [Member]	Common Stock [Member] Issued at $3.80 per share [Member]	Common Stock [Member] Issued at $3.70 per share [Member]	Common Stock [Member] Issued at $4.00 per share [Member]	Common Stock [Member] Issued at $6.23 per share [Member]	Common Stock [Member] Issued at $5.11 per share [Member]	Common Stock [Member] Issued at $2.76 per share [Member]	Common Stock [Member] Issued under Committed Capital Agreement [Member]	Common Stock [Member] Issued @ $2.26 per share [Member]	Common Stock [Member] Issued @ $4.49 per share [Member]	Preferred Stock [Member]	Preferred Stock [Member] Preferred stock issued @ $1,000 per share [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Issued for cash at $10.00 per unit [Member]	Additional Paid-in Capital [Member] Stock issuance cost charged to additional paid-in capital [Member]	Additional Paid-in Capital [Member] Issued for marketable securities at $10.00 per unit [Member]	Additional Paid-in Capital [Member] Issued for cash at $15.00 per unit [Member]	Additional Paid-in Capital [Member] Issued in acquisition [Member]	Additional Paid-in Capital [Member] Issued as a gift for $10.90 per share [Member]	Additional Paid-in Capital [Member] Issued as stock issuance cost at $15.00 per unit [Member]	Additional Paid-in Capital [Member] Exercised at $2.00 per share [Member]	Additional Paid-in Capital [Member] Exercised at $10.00 per share [Member]	Additional Paid-in Capital [Member] Exercised at $15.00 per share [Member]	Additional Paid-in Capital [Member] Issued to purchase Insert Therapeutics share at $39.80 per share [Member]	Additional Paid-in Capital [Member] Issued at $48.80 per share [Member]	Additional Paid-in Capital [Member] Issued at $38.40 per share [Member]	Additional Paid-in Capital [Member] Issued at $35.00 per share [Member]	Additional Paid-in Capital [Member] Issued at $59.10 per share [Member]	Additional Paid-in Capital [Member] Issued to purchase Calando Pharmaceuticals, Inc. at $51.70 per share [Member]	Additional Paid-in Capital [Member] Issued at $57.80 per share, net [Member]	Additional Paid-in Capital [Member] Issued for purchase of Carbon Nanotechnologies, Inc. at $37.70 per share [Member]	Additional Paid-in Capital [Member] Issued at approximately $18.00 per share, net [Member]	Additional Paid-in Capital [Member] Arrowhead's increase in proportionate share of Insert Therapeutics' equity [Member]	Additional Paid-in Capital [Member] Issued at $27.20 per share to Rice University [Member]	Additional Paid-in Capital [Member] Issued at $28.30 per share to purchase shares of Unidym, Inc. [Member]	Additional Paid-in Capital [Member] Issued at $29.50 per share to purchase MASA Energy, LLC [Member]	Additional Paid-in Capital [Member] Issued at $21.90 per share to Unidym for the acquisition of Nanoconduction [Member]	Additional Paid-in Capital [Member] Issued at $21.80 per share [Member]	Additional Paid-in Capital [Member] Issued at $5.50 per share to Unidym Stockholder in exchange for Unidym's shares [Member]	Additional Paid-in Capital [Member] Issued at $5.20 per share to TEL Ventures in exchange for Unidym's shares [Member]	Additional Paid-in Capital [Member] Arrowhead's increase in proportionate share of Calando's equity [Member]	Additional Paid-in Capital [Member] Issued at $3.00 per share [Member]	Additional Paid-in Capital [Member] Series D Preferred Stock Issued for Subscription in Unidym [Member]	Additional Paid-in Capital [Member] Issued to Unidym stockholders in exchange for Unidym's shares [Member]	Additional Paid-in Capital [Member] Issued at $6.30 per share [Member]	Additional Paid-in Capital [Member] Issued at $13.12 per share [Member]	Additional Paid-in Capital [Member] Issued to Calando stockholders in exchange for Calando's Shares [Member]	Additional Paid-in Capital [Member] Issued at $3.80 per share [Member]	Additional Paid-in Capital [Member] Issuance of Common Stock for Subscription [Member]	Additional Paid-in Capital [Member] Issued at $3.70 per share [Member]	Additional Paid-in Capital [Member] Issued at $4.00 per share [Member]	Additional Paid-in Capital [Member] Issued at $6.23 per share [Member]	Additional Paid-in Capital [Member] Issued at $5.11 per share [Member]	Additional Paid-in Capital [Member] Issued at $2.76 per share [Member]	Additional Paid-in Capital [Member] Issued under Committed Capital Agreement [Member]	Additional Paid-in Capital [Member] Preferred stock issued @ $1,000 per share [Member]	Additional Paid-in Capital [Member] Issued @ $2.26 per share [Member]	Additional Paid-in Capital [Member] Issued @ $4.49 per share [Member]	Subscription Receivable [Member]	Subscription Receivable [Member] Series D Preferred Stock Issued for Subscription in Unidym [Member]	Subscription Receivable [Member] Issued to Unidym stockholders in exchange for Unidym's shares [Member]	Subscription Receivable [Member] Issued at $3.80 per share [Member]	Subscription Receivable [Member] Issuance of Common Stock for Subscription [Member]	Subscription Receivable [Member] Issued at $2.76 per share [Member]	Subscription Receivable [Member] Issued @ $2.26 per share [Member]	Accumulated Deficit during Development Stage [Member]	Noncontrolling Interest [Member]	Noncontrolling Interest [Member] Issued to Unidym stockholders in exchange for Unidym's shares [Member]	Noncontrolling Interest [Member] Issued to Calando stockholders in exchange for Calando's Shares [Member]
Beginning Balance Amount at Sep. 30, 2002
Stock issuances		$ 3,000	$ 1,680,000																																											$ 3,000	$ 1,680																																										$ 1,678,320
Issuance and sold of Common Stock																																														300,000	168,000
Stock issuance cost charged to additional paid-in capital				(168,000)																																																																																						(168,000)
Net loss attributable to Arrowhead	(95,238)																																																																																																																																												(95,238)
Ending Balance Amount at Sep. 30, 2003	1,419,762																																												4,680																																											1,510,320																																																					(95,238)
Beginning Balance Shares at Sep. 30, 2003																																													468,000
Stock issuances			475,000		500,000	9,913,182	(150,469)	162,750																																							475	500	6,609	706	163																																						474,525		499,500	9,906,573	(151,175)	162,587
Issuance and sold of Common Stock																																															47,500	50,000	660,879	70,553	15,000	35,623
Stock options exercised, Amount	15,000								534,344	15,000	6,000																																		75							356	75	6																																		14,925							533,988	14,925	5,994
Stock options exercised																																													7,500								7,500	600
Stock issuance cost charged to additional paid-in capital	(991,318)			(96,500)																																																																																				(991,318)		(96,500)
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Total	175,653																																																																																							175,653
Net loss attributable to Arrowhead	(751,255)																																																																																																																																												(2,528,954)	1,777,699
Ending Balance Amount at Sep. 30, 2004	11,227,149																																												13,645																																											12,059,997																																																					(2,624,192)	1,777,699
Ending Balance Shares at Sep. 30, 2004																																													1,363,155
Stock issuances	50,000												2,000,000																																12											502																																49,988											1,999,498
Issuance and sold of Common Stock																																													1,250											50,226
Stock options exercised, Amount											25,000	20,719,335																																										25	13,813																																										24,975	20,705,522
Stock options exercised																																																						2,500	1,381,289
Adjustments to additional paid in capital, reallocation of noncontrolling interest	230,087																																																																																							230,087
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Total	508,513																																																																																							508,513
Net income (loss) attributable to Arrowhead	(6,733,427)																																																																																																																																												(6,854,918)	121,491
Ending Balance Amount at Sep. 30, 2005	28,026,657																																												27,997																																											35,578,580																																																					(9,479,110)	1,899,190
Ending Balance Shares at Sep. 30, 2005																																													2,798,419
Stock issuances														1,000,000	57,600	19,545,000	150,000	1,077,333																																							205	15	5,590	25	208																																							999,795	57,585	19,539,410	149,975	1,077,125
Issuance and sold of Common Stock																																																									20,485	1,500	559,000	2,536	20,838
Stock options exercised, Amount	341,537																																												116																																											341,421
Stock options exercised																																													11,579
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Total	1,369,478																																																																																							1,369,478
Net loss attributable to Arrowhead	(19,961,961)																																																																																																																																												(18,997,209)	(964,752)
Ending Balance Amount at Sep. 30, 2006	31,605,644																																												34,156																																											59,113,369																																																					(28,476,319)	934,438
Ending Balance Shares at Sep. 30, 2006																																													3,414,359
Stock issuances																			15,152,215	5,400,000																																										2,849	1,431																																										15,149,366	5,398,569
Issuance and sold of Common Stock																																																														284,945	143,122
Stock options exercised, Amount	434,727																																												186																																											434,541
Stock options exercised																																													18,616
Adjustments to additional paid in capital, reallocation of noncontrolling interest	2,401,394																																																																																							2,401,394
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Total	2,175,544																																																																																							2,175,544
Net loss attributable to Arrowhead	(30,712,947)																																																																																																																																												(29,931,118)	(781,829)
Ending Balance Amount at Sep. 30, 2007	26,456,577																																												38,622																																											84,672,783																																																					(58,407,437)	152,609
Ending Balance Shares at Sep. 30, 2007																																													3,861,042
Stock issuances																					6,960,585		136,000	200,000	310,000	250,000	32,700																																					3,867	50	71	105	114	15																																						6,956,718		135,950	199,929	309,895	249,886	32,685
Issuance and sold of Common Stock																																																																386,399	5,000	7,055	10,505	11,416	1,500
Stock options exercised, Amount	290,027																																												106																																											289,921
Stock options exercised																																													10,536
Adjustments to additional paid in capital, reallocation of noncontrolling interest																						1,720,962																																																																																						1,720,962
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Total	3,187,397																																																																																							3,187,397
Net loss attributable to Arrowhead	(27,241,639)																																																																																																																																												(27,089,030)	(152,609)
Ending Balance Amount at Sep. 30, 2008	12,302,609																																												42,950																																											97,756,126																																																					(85,496,467)
Ending Balance Shares at Sep. 30, 2008																																													4,293,452
Stock issuances																												1,133,676	1,158,333		2,758,993																																							2,059	2,222	9,197																																										1,131,617	1,156,111		2,749,796
Reclassification of former Unidym mezzanine debt to equity	2,000,000																																																																																							2,000,000
Issuance and sold of Common Stock																																																																						205,839	222,222	919,664
Issuance of preferred stock in subsidiary																																																																																																																						300,000																	(300,000)
Adjustments to additional paid in capital, reallocation of noncontrolling interest	16,297																													2,120,250																																																										16,297																												2,120,250
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Total	2,676,170																																																																																							2,676,170
Amortization of discount on Unidym Series D Preferred Stock																																																																																								163,960																																																					(163,960)
Net loss attributable to Arrowhead	(19,308,392)																																																																																																																																												(19,308,392)
Ending Balance Amount at Sep. 30, 2009	4,857,936																																												56,428																																											110,070,327																																														(300,000)							(104,968,819)
Beginning Balance Shares at Sep. 30, 2009																																													5,641,177
Stock issuances	1,066,050																																3,222,896	3,698,671											2,250																												153	5,083	6,593	1,220												1,063,600																															(1,435)	3,217,813	3,692,078	(160,667)																				200	1,282	159,447
Issuance and sold of Common Stock																																													225,189																												15,318	508,343	659,299	122,000
Stock options exercised, Amount	7,631																																												7																																											7,624
Stock options exercised																																													688
Divestiture of Unidym	300,000																																																																																							245,345																																																						54,655
Issuance of preferred stock in subsidiary																																300,000																																																																																																								300,000
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Total	1,582,149																																																																																							1,582,149
Net loss attributable to Arrowhead	(6,957,038)																																																																																																																																												(5,774,048)	(1,182,990)
Ending Balance Amount at Sep. 30, 2010	8,078,295																																												71,734																																											119,716,834																																																					(110,742,867)	(967,406)
Ending Balance Shares at Sep. 30, 2010																																													7,172,014
Stock issuances	43,279																																			4,643,684									87																																14,574											43,192																																			4,629,110	900,000														(900,000)
Issuance and sold of Common Stock																																													8,656																																1,458,917
Stock options exercised, Amount	13,884																																												27																																											13,857
Stock options exercised																																													2,700
Divestiture of Unidym	254,275																																																																																																																																													254,275
Issuance of preferred stock in subsidiary	1,618,509																																																																																							1,618,509
Adjustments to additional paid in capital, reallocation of noncontrolling interest																																																																																								(849,707)																																																						849,707
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Total	1,404,640																																																																																							1,404,640
Net loss attributable to Arrowhead	(3,492,399)																																																																																																																																												(3,128,885)	(363,514)
Ending Balance Amount at Sep. 30, 2011	12,564,167																																												86,422																																											127,476,435																																														(900,000)							(113,871,752)	(226,938)
Ending Balance Shares at Sep. 30, 2011																																													8,642,286
Stock issuances	50,406						6,147,830																													425,000	2,247,750	400,000	500,001	500,002	5,796,240	1,015,000			16					9,332																											1,382	6,750	1,000	83	98	2,261	689				1	50,390					6,138,498																														523,618		2,241,000	399,000	499,918	499,904	5,809,979	(689)	1,014,999						(100,000)		(16,000)
Issuance and sold of Common Stock																																													15,511					1,217,159																											138,158	675,000	100,000	83,211	97,831	2,260,869	68,926				1,015
Stock options exercised, Amount	23,833																																		8,000										45																																											23,788																																																								8,000
Stock options exercised	4,883																																												4,583
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Total	1,241,404																																																																																							1,241,404
Fractional shares redeemed in reverse stock split																																													(131)
Preferred stock converted to common stock																																													276																																									(1)		(275)
Preferred stock converted to common stock, shares																																													275,782																																									(1,015)
Net loss attributable to Arrowhead	(22,110,723)																																																																																																																																												(21,125,928)	(984,795)
Ending Balance Amount at Sep. 30, 2012	8,808,909																																												108,354																																											145,917,968																																														(1,016,000)							(134,997,680)	(1,203,733)
Ending Balance Shares at Sep. 30, 2012																																													13,579,185
Stock issuances																																											2,178,573	986,049																																								1,826	240																																															2,676,747	985,809							(500,000)
Issuance and sold of Common Stock																																													1,825,079																																							1,825,079	239,894
Stock options exercised	0
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Total	395,675																																																																																							395,675
Subscription payment	16,000																																																																																																																																					16,000
Net income (loss) attributable to Arrowhead	(4,614,159)
Net loss attributable to Arrowhead	(4,780,727)																																																																																																																																												(4,614,159)	(166,568)
Ending Balance Amount at Dec. 31, 2012	$ 7,604,479																																												$ 110,420																																											$ 149,976,199																																														$ (1,500,000)							$ (139,611,839)	$ (1,370,301)
Ending Balance Shares at Dec. 31, 2012																																													15,644,158