Debt - (Credit Facility and Subsequent Amendments - Narrative) (Details)	3 Months Ended		6 Months Ended
	Dec. 31, 2023 USD ($)	Mar. 31, 2022 USD ($)	Sep. 30, 2019 USD ($)	Mar. 31, 2023 USD ($)	Mar. 31, 2022 CAD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2019 CAD ($)	Mar. 31, 2018 USD ($)
Line of Credit
Debt Instrument [Line Items]
Available lines of credit	$ 839,632,000			$ 693,444,000
Amended Credit Facility, due 2022 | Secured Debt
Debt Instrument [Line Items]
Debt instrument, face amount								$ 150,000,000
Amended 2017 Term Loan | Secured Debt
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity						$ 449,105,000
Change in face amount			$ (299,105,000)
Amended 2017 Term Loan, Canadian Dollars | Secured Debt
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity						99,105,000	$ 133,050,000
Amended 2017 Revolver | Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity						$ 700,000,000
Second Amended Term Loan | Secured Debt
Debt Instrument [Line Items]
Debt instrument, face amount		$ 130,000,000
Change in face amount		150,000,000
Available lines of credit	197,277,000
Second Amended Term Loan | Secured Debt | Redemption Period One
Debt Instrument [Line Items]
Debt instrument, periodic payment	2,630,000
Second Amended Term Loan | Secured Debt | Redemption Period Two
Debt Instrument [Line Items]
Debt instrument, periodic payment	3,946,000
Second Amended Term Loan | Secured Debt | Redemption Period Three
Debt Instrument [Line Items]
Debt instrument, periodic payment	5,261,000
Second Amended Term Loan | Secured Debt | Debt Instrument, Redemption, Period Four
Debt Instrument [Line Items]
Debt instrument, periodic payment	$ 157,821,000
Second Amended Term Loan, Canadian Dollars | Secured Debt
Debt Instrument [Line Items]
Debt instrument, face amount		84,229,000			$ 106,440,000
Third Amended Term Loan
Debt Instrument [Line Items]
Debt instrument, covenant, leverage ratio	4.50
Debt instrument, covenant, leverage ratio	4.00
Third Amended Term Loan | Minimum
Debt Instrument [Line Items]
Debt instrument, covenant, leverage ratio	4.00
Debt instrument, covenant, leverage ratio	3.50
Third Amended Term Loan | Maximum
Debt Instrument [Line Items]
Debt instrument, covenant, leverage ratio	4.25
Consideration transferred	$ 250,000,000
Debt instrument, covenant, leverage ratio	4.25
Third Amended Term Loan | Secured Debt
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity				300,000,000
Capitalized debt issuance costs				1,161,000
Deferred asset				1,096,000
Long-term debt				$ 300,000,000
Third Amended Term Loan | Secured Debt | Secured Overnight Financing Rate
Debt Instrument [Line Items]
Basis spread on variable rate	1000.00%
Third Amended Term Loan | Secured Debt | Secured Overnight Financing Rate | Net Leverage Ratio
Debt Instrument [Line Items]
Basis spread on variable rate	1.50%
Third Amended Term Loan | Secured Debt | Federal Funds Effective Rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
Third Amended Term Loan | Secured Debt | Eurocurrency Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
Third Amended Term Loan | Secured Debt | Minimum
Debt Instrument [Line Items]
Commitment fee percentage	0.175%
Third Amended Term Loan | Secured Debt | Minimum | Secured Overnight Financing Rate
Debt Instrument [Line Items]
Basis spread on variable rate	1.375%
Third Amended Term Loan | Secured Debt | Minimum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.375%
Third Amended Term Loan | Secured Debt | Maximum
Debt Instrument [Line Items]
Commitment fee percentage	0.35%
Third Amended Term Loan | Secured Debt | Maximum | Secured Overnight Financing Rate
Debt Instrument [Line Items]
Basis spread on variable rate	2.50%
Third Amended Term Loan | Secured Debt | Maximum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate	1.50%
Third Amended Term Loan | Secured Debt | Redemption Period One
Debt Instrument [Line Items]
Debt instrument, periodic payment	$ 3,750,000
Third Amended Term Loan | Secured Debt | Redemption Period Two
Debt Instrument [Line Items]
Debt instrument, periodic payment	5,625,000
Third Amended Term Loan | Secured Debt | Redemption Period Three
Debt Instrument [Line Items]
Debt instrument, periodic payment	7,500,000
Third Amended Term Loan | Secured Debt | Debt Instrument, Redemption, Period Four
Debt Instrument [Line Items]
Debt instrument, periodic payment	$ 232,500,000
Second Amended Credit Facility | Fourth Amended Credit Facility, due 2026
Debt Instrument [Line Items]
Percentage of capital stock collateralizing debt	65.00%
Second Amended Credit Facility | Fourth Amended Credit Facility, due 2026 | Secured Overnight Financing Rate
Debt Instrument [Line Items]
Basis spread on variable rate	1.25%
Second Amended Credit Facility | Fourth Amended Credit Facility, due 2026 | Federal Funds Effective Rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
Second Amended Credit Facility | Fourth Amended Credit Facility, due 2026 | Eurocurrency Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
Second Amended Credit Facility | Fourth Amended Credit Facility, due 2026 | CDOR
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
Second Amended Credit Facility | Fourth Amended Credit Facility, due 2026 | Minimum | Secured Overnight Financing Rate
Debt Instrument [Line Items]
Basis spread on variable rate	1.125%
Second Amended Credit Facility | Fourth Amended Credit Facility, due 2026 | Maximum | Secured Overnight Financing Rate
Debt Instrument [Line Items]
Basis spread on variable rate	2.25%
Revolving Credit Facility | Amended Credit Facility, due 2022 | Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity								$ 600,000,000
Revolving Credit Facility | Amended 2017 Revolver | Line of Credit
Debt Instrument [Line Items]
Change in borrowing capacity			$ 100,000,000
Revolving Credit Facility | Second Amended Revolver | Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		850,000,000
Change in borrowing capacity		$ 150,000,000
Available lines of credit	$ 100,000,000
Revolving Credit Facility | Third Amended Term Loan | Line of Credit
Debt Instrument [Line Items]
Available lines of credit	288,750,000
Revolving Credit Facility | Fourth Amended Credit Facility | Fourth Amended Credit Facility, due 2026
Debt Instrument [Line Items]
Optional increase in line of credit maximum borrowing capacity	$ 350,000,000