Long Term Debt (Narrative) (Details) - USD ($)	9 Months Ended
	Jun. 30, 2016	Sep. 30, 2015	Oct. 31, 2001
U.S. Revolver
Line Of Credit Facility [Line Items]
Revolving credit facility		$ 75,000,000
Revolving credit interest rate	The interest rate for amounts outstanding under the Amended Credit Agreement for the U.S. Revolver is a floating rate based upon the higher of the Federal Funds Rate plus 0.5%, the bank’s prime rate, or the Eurocurrency rate plus 1.00%.
Outstanding letters of credit	$ 26,800,000
Amount of credit facility remaining borrowing capacity	$ 48,200,000
Credit facility expiration date	Dec. 31, 2018
Revolving credit facility borrowings, outstanding amount	$ 0
Percentage of voting capital stock pledged as collateral	100.00%
Non-domestic subsidiaries of voting capital stock	65.00%
U.S. Revolver | Maximum
Line Of Credit Facility [Line Items]
Basis spread on variable rate	1.75%
U.S. Revolver | Federal Funds Rate
Line Of Credit Facility [Line Items]
Basis spread on variable rate	0.50%
U.S. Revolver | Eurocurrency Rate
Line Of Credit Facility [Line Items]
Basis spread on variable rate	1.00%
Canadian Revolver
Line Of Credit Facility [Line Items]
Revolving credit facility	$ 7,700,000
Outstanding letters of credit	0
Amount of credit facility remaining borrowing capacity	$ 7,700,000
Credit facility expiration date	Mar. 31, 2018
Revolving credit facility borrowings, outstanding amount	$ 0
Canadian Revolver | Maximum
Line Of Credit Facility [Line Items]
Basis spread on variable rate	1.75%
Canadian Revolver | Minimum
Line Of Credit Facility [Line Items]
Basis spread on variable rate	0.50%
Industrial Development Revenue Bonds
Line Of Credit Facility [Line Items]
Borrowings			$ 8,000,000
Reimbursement agreement requires annual redemptions	$ 400,000
Interest rate	0.58%