Debt - Amended credit agreement (Details) | Dec. 31, 2018USD ($) | Dec. 31, 2020 | Mar. 31, 2020 | Dec. 31, 2019 | Sep. 30, 2019USD ($)Lender | Jun. 30, 2020 | Sep. 30, 2020 | Sep. 30, 2019USD ($)Lender | Nov. 30, 2020USD ($) |
Line of Credit Facility [Line Items] | | | | | | | | | |
Interest coverage ratio | | | | | | | | 3 | |
Maximum leverage ratio | | | | | | | | 4.25 | |
Maximum senior secured ratio | | | | | | | | 2.50 | |
Line of credit | London Interbank Offered Rate (LIBOR) | Minimum | United States of America, Dollars | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Debt instrument, basis spread on variable rate | 2.25% | | | | | | | | |
Line of credit | London Interbank Offered Rate (LIBOR) | Maximum | United States of America, Dollars | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Debt instrument, basis spread on variable rate | 4.00% | | | | | | | | |
Line of credit | Base rate | Minimum | United States of America, Dollars | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Debt instrument, basis spread on variable rate | 1.25% | | | | | | | | |
Line of credit | Base rate | Minimum | Canada, Dollars | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Debt instrument, basis spread on variable rate | 1.25% | | | | | | | | |
Line of credit | Base rate | Maximum | United States of America, Dollars | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Debt instrument, basis spread on variable rate | 3.00% | | | | | | | | |
Line of credit | Base rate | Maximum | Canada, Dollars | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Debt instrument, basis spread on variable rate | 3.00% | | | | | | | | |
Line of credit | Canadian Dealer Offered Rate (CDOR) | Minimum | Canada, Dollars | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Debt instrument, basis spread on variable rate | 2.25% | | | | | | | | |
Line of credit | Canadian Dealer Offered Rate (CDOR) | Maximum | Canada, Dollars | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Debt instrument, basis spread on variable rate | 4.00% | | | | | | | | |
Line of credit | Bank Bill Swap Bid Rate (BBSY) | Minimum | Australia, Dollars | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Debt instrument, basis spread on variable rate | 2.25% | | | | | | | | |
Line of credit | Bank Bill Swap Bid Rate (BBSY) | Maximum | Australia, Dollars | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Debt instrument, basis spread on variable rate | 4.00% | | | | | | | | |
Amended credit facility | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Maximum leverage ratio | | | | | 4.25 | | | | |
Number of lenders | Lender | | | | | 10 | | | 10 | |
Amended credit facility | Minimum | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Lender commitments, within credit agreement | | | | | $ 24,900,000 | | | $ 24,900,000 | |
Amended credit facility | Maximum | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Lender commitments, within credit agreement | | | | | 85,400,000 | | | 85,400,000 | |
Amended credit facility | US term loan | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Term loan, face amount | | | | | 285,400,000 | | | 285,400,000 | |
Amended credit facility | Amended credit facility | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Revolving credit facility | | | | | 24,000,000 | | | 24,000,000 | |
Revolving credit facility | Amended credit facility | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Revolving credit facility, maximum borrowing capacity | | | | | 239,500,000 | | | 239,500,000 | |
Revolving credit facility, U.S. subsidiaries | Amended credit facility | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Revolving credit facility, maximum borrowing capacity | | | | | 20,000,000 | | | 20,000,000 | |
Outstanding letters of credit | | | | | 300,000 | | | 300,000 | |
Revolving credit facility, Canadian subsidiaries | Amended credit facility | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Revolving credit facility, maximum borrowing capacity | | | | | 159,500,000 | | | 159,500,000 | |
Outstanding letters of credit | | | | | 1,200,000 | | | 1,200,000 | |
Revolving credit facility, Australian subsidiaries | Amended credit facility | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Revolving credit facility, maximum borrowing capacity | | | | | 60,000,000 | | | 60,000,000 | |
Outstanding letters of credit | | | | | $ 500,000 | | | 500,000 | |
Maximum Leverage Ratio | Revolving credit facility, Australian subsidiaries | Amended And Restated Syndicated Facility Agreement | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Gross proceeds from qualified offering of indebtedness | $ 150,000,000 | | | | | | | $ 150,000,000 | |
Offering of Indebtedness | Amended credit facility | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Maximum leverage ratio | | | | | 4.25 | | | | |
Scenario, Forecast | Amended credit facility | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Maximum leverage ratio | | 3.50 | 3.75 | 4 | | 3.75 | 3.75 | | |
Scenario, Forecast | Offering of Indebtedness | Amended credit facility | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Maximum leverage ratio | | | | 4 | | | | | |
Subsequent Event | First non-extending lender | Amended credit facility | Canadian term loans | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Notes Payable | | | | | | | | | $ 6,900,000 |
Subsequent Event | Revolving credit facility, U.S. subsidiaries | Second non-extending lender | Amended credit facility | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Revolving credit facility | | | | | | | | | 7,400,000 |
Subsequent Event | Revolving credit facility, Canadian subsidiaries | Amended credit facility | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Revolving credit facility, maximum borrowing capacity | | | | | | | | | 183,500,000 |
Subsequent Event | Revolving credit facility, Canadian subsidiaries | First non-extending lender | Amended credit facility | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Revolving credit facility | | | | | | | | | 15,700,000 |
Subsequent Event | Revolving credit facility, Canadian subsidiaries | Second non-extending lender | Amended credit facility | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Revolving credit facility | | | | | | | | | 22,500,000 |
Subsequent Event | Revolving credit facility, Australian subsidiaries | First non-extending lender | Amended credit facility | | | | | | | | | |
Line of Credit Facility [Line Items] | | | | | | | | | |
Revolving credit facility | | | | | | | | | $ 10,400,000 |