Employee Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Retirement Benefits [Abstract]
Service cost	$ 1,125	$ 898	$ 933
Interest cost	492	699	742
Expected return on plan assets	(387)	(440)	(470)
Amortization of actuarial losses	1,006	371	299
Pension expense for defined benefit plans	$ 2,236	$ 1,528	$ 1,504