Research, License, Supply and other Agreements - Additional Information (Detail) (USD $)	12 Months Ended						1 Months Ended	3 Months Ended	12 Months Ended
	Sep. 30, 2013 Milestone	Sep. 30, 2013 CNS [Member]	Sep. 30, 2012 CNS [Member]	Sep. 30, 2011 CNS [Member]	Sep. 30, 2013 CNS [Member] Minimum [Member]	Sep. 30, 2013 CNS [Member] Maximum [Member]	Aug. 31, 2007 Azur Pharma [Member]	Sep. 30, 2013 Azur Pharma [Member]	Sep. 30, 2012 Azur Pharma [Member]	Sep. 30, 2011 Azur Pharma [Member]	Sep. 30, 2013 Merck [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone paid upon FDA approval of NUEDEXTA				$ 75,000
Royalties recorded to cost of product sales		3,500,000	1,800,000	309,000,000
Percentage of royalty payable under agreement					5.00%	8.00%
Individual milestone range for each accepted NDA					75,000	125,000
Maximum milestone payments		1,100,000
Maximum number of milestones required to make payment	10
Number of basis for achievements of milestones	5
Milestone and royalty payments clinical, minimum	2,000,000
Milestone and royalty payments clinical, maximum	6,000,000
Milestone and royalty payments regulatory, minimum	1,500,000
Milestone and royalty payments regulatory, maximum	15,000,000
Milestone and royalty payments commercial targets, minimum	25,000,000
Milestone and royalty payments commercial targets, maximum	60,000,000
Milestone and royalty payments, aggregate	200,000,000
Royalty payments are tiered, minimum	1,000,000,000
Paid milestone agreement expenses	2,000,000
Up-front cash payment	20,000,000
Maximum additional payments from future milestones	90,000,000
Agreement date											Oct. 01, 2013
Agreement period term											3 years
Maximum revenue to be received											60,000,000
Agreement termination period											90 days
Royalty receivable under agreement, Maximum							2,000,000	2,000,000	492,000	527,000
Recognized royalty revenue from product sales							$ 17,000,000		$ 17,000,000
Annualized net product revenues							3.00%