Retirement and Other Benefit Plans - Schedule Of Net periodic benefit cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Retirement and Other Benefit Plans
Service cost	$ 0	$ 0	$ 0
Interest cost	3,700	3,400	3,200
Expected return on plan assets	(4,400)	(3,800)	(3,900)
Net actuarial loss	2,100	2,300	2,600
Net periodic benefit cost	1,400	1,900	1,900
Defined contribution plans	7,300	7,100	6,300
Total	$ 8,700	$ 9,000	$ 8,200