Fair Value Measurements (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Assets:
Cash and cash equivalents	$ 160,216	$ 118,639
Short-term investments	18,705	6,042
Other assets	7,351	6,825
Liabilities:
Deferred compensation	6,569	6,249
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	160,216	118,639
Short-term investments	18,705	6,042
Other assets	0	0
Liabilities:
Deferred compensation	0	0
Significant Other Observable Inputs (Level 2)
Assets:
Cash and cash equivalents	0	0
Short-term investments	0	0
Other assets	7,351	6,825
Liabilities:
Deferred compensation	6,569	6,249
Significant Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	0	0
Short-term investments	0	0
Other assets	0	0
Liabilities:
Deferred compensation	$ 0	$ 0