Pension Plan and Retirement Benefits - Defined Benefit Plans - Recognized in BS (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Accrued pension and postretirement benefits:
Current	$ (5,095)	$ (4,965)
Non-current	(250,251)	(212,872)
Accrued pension and postretirement benefits	(255,346)	(217,837)
Accumulated other comprehensive loss:
Net (gain) loss	164,024	132,445
Prior service cost	3,020	3,828
Total accumulated other comprehensive loss	167,044	136,273
Amounts expected to be recognized from AOCI into the statement of operations in the following year:
Amortization of net loss	15,546	11,663
Amortization of prior service cost	808	808
Total	16,354	12,471
Accumulated benefit obligation	317,754	299,039
Defined Benefit Pension Plans
Accrued pension and postretirement benefits:
Non-current	(129,375)	(106,445)
Accrued pension and postretirement benefits	(129,375)	(106,445)
Accumulated other comprehensive loss:
Net (gain) loss	116,388	97,268
Prior service cost	3,020	3,828
Total accumulated other comprehensive loss	119,408	101,096
Amounts expected to be recognized from AOCI into the statement of operations in the following year:
Amortization of net loss	11,268	8,838
Amortization of prior service cost	808	808
Total	12,076	9,646
Postretirement Health Care Benefits
Accrued pension and postretirement benefits:
Current	(5,000)	(4,870)
Non-current	(120,117)	(105,664)
Accrued pension and postretirement benefits	(125,117)	(110,534)
Accumulated other comprehensive loss:
Net (gain) loss	47,636	35,177
Total accumulated other comprehensive loss	47,636	35,177
Amounts expected to be recognized from AOCI into the statement of operations in the following year:
Amortization of net loss	4,278	2,825
Total	4,278	2,825
Non-qualified pension plan
Accrued pension and postretirement benefits:
Current	(95)	(95)
Non-current	(759)	(763)
Accrued pension and postretirement benefits	$ (854)	$ (858)