Debt (Narratives) (Details) - USD ($)		3 Months Ended		12 Months Ended
	Aug. 09, 2019	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Nov. 03, 2020	Jun. 30, 2020	May 08, 2020
Line Of Credit Facility [Line Items]
Outstanding letters of credit		$ 14,800,000
Interest Expense
Line Of Credit Facility [Line Items]
Amortization of deferred financing costs		$ 800,000	$ 800,000
2019 Credit Agreement
Line Of Credit Facility [Line Items]
Deferred financing cost						$ 10,500,000
Amortization of deferred financing costs	$ 1,600,000
Debt instrument interest rate		2.40%	4.90%
2019 Credit Agreement | First Amendment
Line Of Credit Facility [Line Items]
Amendment start date		Apr. 08, 2020
2019 Credit Agreement | Second Amendment
Line Of Credit Facility [Line Items]
Amendment start date		May 08, 2020
2019 Credit Agreement | Third Amendment
Line Of Credit Facility [Line Items]
Amendment start date		Nov. 03, 2020
Line of credit sublimit for letters of credit					$ 20,000,000.0
2019 Credit Agreement | Fourth Amendment
Line Of Credit Facility [Line Items]
Amendment start date		Dec. 08, 2020
2019 Credit Agreement | Term Loan
Line Of Credit Facility [Line Items]
Credit Facility, term	5 years
Borrowing capacity from Credit Agreement	$ 380,000,000
2019 Credit Agreement | Revolving Facility
Line Of Credit Facility [Line Items]
Credit Facility, term	5 years
Borrowing capacity from Credit Agreement	$ 75,000,000	$ 55,000,000.0
Repayments of Lines of Credit		12,000,000		$ 55,000,000.0
Line of credit facility remaining outstanding balance		0
Borrowing capacity from Credit Agreement		$ 60,200,000
2019 Credit Agreement | Revolving Facility | Second Amendment
Line Of Credit Facility [Line Items]
Borrowing capacity from Credit Agreement							$ 55,000,000.0
2019 Credit Agreement | Revolving Facility | Applicable Margin for Eurodollar | Second Amendment
Line Of Credit Facility [Line Items]
Euro dollar rate							4.50%
Initial Term Loan | Revolving Facility
Line Of Credit Facility [Line Items]
Base rate	0.00%
Commitment fee	0.30%
Amendments
Line Of Credit Facility [Line Items]
Deferred financing cost						$ 1,500,000
Maximum | 2019 Credit Agreement
Line Of Credit Facility [Line Items]
Additional incremental loan facility that may be requested	$ 100,000,000
Maximum | 2019 Credit Agreement | Applicable Margin for Eurodollar | Second Amendment
Line Of Credit Facility [Line Items]
Commitment fee		0.40%
Suspension period rate		4.50%
Maximum | Initial Term Loan | Applicable Margin for Eurodollar
Line Of Credit Facility [Line Items]
Borrowings, interest rate	3.50%
Maximum | Initial Term Loan | Applicable Margin for Base Rate
Line Of Credit Facility [Line Items]
Borrowings, interest rate	2.50%
Maximum | Initial Term Loan | Revolving Facility
Line Of Credit Facility [Line Items]
Commitment fee	0.40%
Minimum | 2019 Credit Agreement | Applicable Margin for Eurodollar | Second Amendment
Line Of Credit Facility [Line Items]
Commitment fee		0.35%
Ongoing rate		2.75%
Minimum | Initial Term Loan | Applicable Margin for Eurodollar
Line Of Credit Facility [Line Items]
Borrowings, interest rate	1.25%
Minimum | Initial Term Loan | Applicable Margin for Base Rate
Line Of Credit Facility [Line Items]
Borrowings, interest rate	0.25%
Minimum | Initial Term Loan | Revolving Facility
Line Of Credit Facility [Line Items]
Commitment fee	0.25%