Commitments and Contingencies (Schedule of Letters of Credit and Surety Bonds) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Jun. 30, 2022	Jun. 30, 2022	Sep. 30, 2021
Other Commitments [Line Items]
Revolving credit capacity	$ 60,000	$ 60,000	$ 60,000
Remaining revolving credit capacity	50,471	50,471	49,888
Surety Bond
Other Commitments [Line Items]
Surety capacity	262,090	262,090	250,000
Surety issuances	129,021	129,021	147,845
Remaining surety available	$ 133,069	133,069	102,155
Minimum | Surety Bond
Other Commitments [Line Items]
Letter of Credit, Guarantee, Bond Commitments, Expiration Period	12 months
Maximum | Surety Bond
Other Commitments [Line Items]
Letter of Credit, Guarantee, Bond Commitments, Expiration Period	10 years
Letter of Credit
Other Commitments [Line Items]
Letters of credit outstanding, amount	$ 9,529	9,529	10,112
Remaining revolving credit capacity	$ 129,471	$ 129,471	$ 302,888
Debt Instrument, Maturity Date		Mar. 20, 2030