Fair Value Measurements Using Significant Unobservable Inputs Level 3 (Detail) (USD $)	2 Months Ended	3 Months Ended
	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Modification of Warrants	$ 1,300,170	$ (1,300,170)	$ 0
Exercises of Warrants	224,000arth_GainOnExerciseOfWarrants	224,000arth_GainOnExerciseOfWarrants	0arth_GainOnExerciseOfWarrants
Adjustments to estimated fair value		7,541,693
Ending balance at December 31, 2014	4,593,000	4,593,000
Fair Value, Inputs, Level 3
Beginning balance at September 30, 2014		6,270,000
Modification of Warrants		1,300,170
Exercises of Warrants		(224,000)
Adjustments to estimated fair value		(2,753,170)
Ending balance at December 31, 2014	$ 4,593,000	$ 4,593,000