Accounts receivable (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at Beginning of Period	$ 1,408	$ 1,868	$ 1,681
Deductions	568	1,294	847
Balance at End of Period	1,588	1,408	1,868
Charged to Cost and Expenses
Accounts, Notes, Loans and Financing Receivable [Line Items]
Additions	$ 748	$ 834	$ 1,034