Annual report pursuant to Section 13 and 15(d)

Debt - Narrative (Details)

v3.5.0.2
Debt - Narrative (Details)
CAD in Millions
12 Months Ended
Sep. 30, 2016
USD ($)
period
letter_of_credit
Sep. 30, 2015
USD ($)
Sep. 30, 2014
USD ($)
Sep. 30, 2016
CAD
period
letter_of_credit
Debt Instrument [Line Items]        
Interest expense $ 4,134,000 $ 1,398,000 $ 0  
Credit Agreement Expiring January 2020        
Debt Instrument [Line Items]        
Maximum borrowing capacity $ 400,000,000      
Leverage ratio 2.5      
Total leverage ratio (less than) 1      
Accrued interest rate (as a percent) 1.55%     1.55%
Fixed payment of principal balance $ 42,000,000      
Interest paid 3,700,000      
Credit Agreement Expiring January 2020 | U.S Dollar Borrowings        
Debt Instrument [Line Items]        
Borrowings $ 164,700,000      
Credit Agreement Expiring January 2020 | Minimum | Base Rate        
Debt Instrument [Line Items]        
Margin (as a percent) 0.00%      
Credit Agreement Expiring January 2020 | Minimum | Eurocurrency Rate        
Debt Instrument [Line Items]        
Margin (as a percent) 1.00%      
Credit Agreement Expiring January 2020 | Minimum | Index Rate        
Debt Instrument [Line Items]        
Margin (as a percent) 1.00%      
Credit Agreement Expiring January 2020 | Maximum | Base Rate        
Debt Instrument [Line Items]        
Margin (as a percent) 0.75%      
Credit Agreement Expiring January 2020 | Maximum | Eurocurrency Rate        
Debt Instrument [Line Items]        
Margin (as a percent) 1.75%      
Credit Agreement Expiring January 2020 | Maximum | Index Rate        
Debt Instrument [Line Items]        
Margin (as a percent) 1.75%      
Swingline loans        
Debt Instrument [Line Items]        
Maximum borrowing capacity $ 5,000,000      
Letters of credit        
Debt Instrument [Line Items]        
Maximum borrowing capacity $ 30,000,000      
Number of letters of credit issued | letter_of_credit 3     3
Outstanding borrowings $ 5,200,000      
Letters of credit | Minimum        
Debt Instrument [Line Items]        
Leverage ratio to calculate annual commitment fee (as a percent) 0.15%      
Letters of credit | Maximum        
Debt Instrument [Line Items]        
Leverage ratio to calculate annual commitment fee (as a percent) 0.30%      
Atlantic Innovation Fund of Canada        
Debt Instrument [Line Items]        
Borrowings $ 800,000     CAD 1.0
Interest expense $ 0      
Number of remaining quarterly installments | period 23     23
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