Commitments and Contingencies (Schedule of Letters of Credit and Surety Bonds) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2020	Sep. 30, 2019
Other Commitments [Line Items]
Debt instrument, unused borrowing capacity, amount	$ 33,128	$ 32,044
Line of credit facility, remaining borrowing capacity	45,000	45,000
Surety Bond [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	230,000	220,000
Guarantor Obligations, Current Carrying Value	148,108	144,717
Guarantor Obligations, Remaining Surety Bonds Available	$ 81,892	75,283
Minimum | Surety Bond [Member]
Other Commitments [Line Items]
Letter of Credit, Guarantee, Bond Commitments, Expiration Period	12 months
Maximum | Surety Bond [Member]
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	$ 11,872	12,956
Debt instrument, unused borrowing capacity, amount	$ 113,128	$ 112,044