Quarterly report pursuant to Section 13 or 15(d)

Debt (Details)

v3.7.0.1
Debt (Details)
CAD in Millions
6 Months Ended
Mar. 31, 2017
USD ($)
period
letter_of_credit
Mar. 31, 2016
USD ($)
Mar. 31, 2017
CAD
period
letter_of_credit
Debt Instrument [Line Items]      
Debt outstanding $ 34,000,000    
Credit Agreement Expiring January 2020      
Debt Instrument [Line Items]      
Maximum borrowing capacity $ 400,000,000    
Dividend payment restriction ratio (less than) 2.5    
Total leverage ratio (less than) 1    
Interest paid $ 1,600,000 $ 1,700,000  
Credit Agreement Expiring January 2020 | U.S Dollar Borrowings      
Debt Instrument [Line Items]      
Amount borrowed $ 115,000,000    
Letters of Credit      
Debt Instrument [Line Items]      
Number of letters of credit issued | letter_of_credit 2   2
Outstanding borrowings $ 700,000    
Letters of Credit (Other than Revolving Credit Agreement)      
Debt Instrument [Line Items]      
Number of letters of credit issued | letter_of_credit 2   2
Outstanding borrowings $ 3,000,000    
Atlantic Innovation Fund of Canada      
Debt Instrument [Line Items]      
Number of remaining quarterly installments | period 21   21
Atlantic Innovation Fund of Canada | Canadian Dollar Borrowings      
Debt Instrument [Line Items]      
Amount borrowed $ 700,000   CAD 0.9