Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019
Assets:
Cash and cash equivalents	$ 120,966	$ 118,639
Short-term investments		6,042
Other assets	7,205	6,825
Liabilities:
Deferred compensation	6,869	6,249
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	120,966	118,639
Short-term investments		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
Other assets	7,205	6,825
Liabilities:
Deferred compensation	6,869	6,249
Significant Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	0	0
Short-term investments		0
Other assets	0	0
Liabilities:
Deferred compensation	$ 0	$ 0