Components of Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Pension
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 1,780	$ 1,905	$ 3,560	$ 3,811
Interest cost	2,129	2,111	4,258	4,222
Expected return on plan assets	(4,815)	(6,202)	(9,630)	(12,405)
Amortization of Prior service cost	0	0	0	0
Amortization of Net loss	707	2,750	1,414	5,499
Net periodic cost (income)	(199)	564	(398)	1,127
RIM
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	61	59	122	119
Interest cost	111	107	222	215
Expected return on plan assets	0	0	0	0
Amortization of Prior service cost	0	0	0	0
Amortization of Net loss	103	113	206	227
Net periodic cost (income)	275	279	550	561
Post-retirement
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	93	118	186	236
Interest cost	205	186	410	371
Expected return on plan assets	0	0	0	0
Amortization of Prior service cost	(34)	(34)	(68)	(68)
Amortization of Net loss	69	81	138	163
Net periodic cost (income)	$ 333	$ 351	$ 666	$ 702