Fair Value Measurements Using Significant Unobservable Inputs Level 3 (Detail) (USD $)	3 Months Ended		6 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
Beginning balance at September 30, 2014			$ 6,270,000
Modification of Warrants	624,016		1,924,186
Exercises of Warrants	0arth_GainOnExerciseOfWarrants	0arth_GainOnExerciseOfWarrants	224,000arth_GainOnExerciseOfWarrants	0arth_GainOnExerciseOfWarrants
Adjustments to estimated fair value	0	(7,541,693)	0	(7,541,693)
Ending balance at March 31, 2015	4,213,595		4,213,595
Fair Value, Inputs, Level 3
Beginning balance at September 30, 2014			6,270,000
Modification of Warrants			1,924,186
Exercises of Warrants			(224,000)
Adjustments to estimated fair value			(3,756,591)
Ending balance at March 31, 2015	$ 4,213,595		$ 4,213,595