Employee Benefits - Additional Information (Details) (401(k) Retirement Plan, USD $) In Millions, unless otherwise specified	12 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
401(k) Retirement Plan
Employee Benefits (Textual) [Abstract]
Company's share of discretionary matching contributions	$ 1.1	$ 0.9	$ 0.7

Amount of discretionary contributions made by an employer to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration