Fair Value Measurements (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Sep. 30, 2019
Assets:
Cash and cash equivalents	$ 156,026	$ 118,639
Short-term investments	7,330	6,042
Other assets	6,997	6,825
Liabilities:
Deferred compensation	6,370	6,249
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	156,026	118,639
Short-term investments	7,330	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	6,997	6,825
Liabilities:
Deferred compensation	6,370	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