Pension Plan and Retirement Benefits (Details 2) - USD ($) $ in Thousands		1 Months Ended	12 Months Ended
	Jan. 01, 2007	Mar. 31, 2006	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Pension Plan and Retirement Benefits
Maximum liability related to total retiree health care costs under plan amendment	$ 5,000
Change in Plan Assets:
Fair value of plan assets at end of year			$ 205,498
Accrued pension and postretirement benefits:
Current			(4,965)	$ (4,572)
Non-current			(212,872)	(173,225)
Accrued pension and postretirement benefits			(217,837)	(177,797)
Accumulated other comprehensive loss:
Net loss			132,445	97,155
Prior service cost			3,828	4,636
Total accumulated other comprehensive loss			136,273	101,791
Amounts expected to be recognized from AOCI into the statement of operations in the following year:
Amortization of net loss			11,663	7,079
Amortization of prior service cost			808	808
Total			12,471	7,887
Accumulated benefit obligation			299,039	276,009
Pension Plan, Defined Benefit
Change in Benefit Obligation:
Projected benefit obligation at beginning of year			288,559	273,693
Service cost			3,898	3,971	$ 4,881
Interest cost			11,203	11,989	10,839
Actuarial losses (gains)			(21,861)	(12,143)
Benefits paid			(13,578)	(13,237)
Projected benefit obligation at end of year			311,943	288,559	273,693
Change in Plan Assets:
Fair value of plan assets at beginning of year			216,962	206,113
Actual return on assets			(295)	21,861
Employer contribution			2,409	2,225
Benefits paid			(13,578)	(13,237)
Fair value of plan assets at end of year			205,498	216,962	206,113
Funded Status of Plan:
Unfunded status			(106,445)	(71,597)
Accrued pension and postretirement benefits:
Non-current			(106,445)	(71,597)
Accrued pension and postretirement benefits			(106,445)	(71,597)
Accumulated other comprehensive loss:
Net loss			97,268	64,641
Prior service cost			3,828	4,636
Total accumulated other comprehensive loss			101,096	69,277
Amounts expected to be recognized from AOCI into the statement of operations in the following year:
Amortization of net loss			8,838	4,645
Amortization of prior service cost			808	808
Total			9,646	5,453
Components of net periodic pension cost and postretirement health care benefit cost
Service cost			3,898	3,971	4,881
Interest cost			11,203	11,989	10,839
Expected return			(15,117)	(15,033)	(13,189)
Amortization of prior service cost			808	808	808
Recognized actuarial loss			4,645	4,612	10,189
Net periodic benefit cost			5,437	6,347	$ 13,528
Pension Plan, Defined Benefit | Subsidiaries
Change in Plan Assets:
Employer contribution			909	975
US pension plan
Change in Plan Assets:
Fair value of plan assets at beginning of year			197,330
Employer contribution			1,500	1,250
Fair value of plan assets at end of year			$ 186,438	$ 197,330
Assumptions used to determine benefit obligation
Discount rate (as a percent)			4.00%	4.00%
Rate of compensation increase (as a percent)			3.50%	3.50%
Assumptions used to determine net periodic benefit cost
Discount rate (as a percent)			4.00%	4.50%	3.625%
Expected return on plan assets (as a percent)			7.50%	7.50%	7.50%
Rate of compensation increase (as a percent)			3.50%	3.50%	3.50%
UK pension plan
Change in Plan Assets:
Fair value of plan assets at beginning of year			$ 19,632
Fair value of plan assets at end of year			$ 19,060	$ 19,632
Assumptions used to determine benefit obligation
Discount rate (as a percent)			3.70%	3.90%
Assumptions used to determine net periodic benefit cost
Discount rate (as a percent)			3.90%	4.30%	4.10%
Expected return on plan assets (as a percent)			4.40%	4.80%	4.20%
Postretirement health care
Pension Plan and Retirement Benefits
Maximum liability related to total retiree health care costs under plan amendment	$ 5,000
Reduction in accumulated postretirement benefit liability due to plan amendment		$ 46,313
Period of amortization as a reduction to expense		8 years
Change in Benefit Obligation:
Projected benefit obligation at beginning of year			$ 105,387	$ 98,772
Service cost			337	267	$ 387
Interest cost			4,385	4,578	4,330
Actuarial losses (gains)			(5,097)	(5,614)
Benefits paid			(4,672)	(3,844)
Projected benefit obligation at end of year			110,534	105,387	98,772
Change in Plan Assets:
Employer contribution			4,672	3,844
Benefits paid			(4,672)	(3,844)
Funded Status of Plan:
Unfunded status			(110,534)	(105,387)
Accrued pension and postretirement benefits:
Current			(4,870)	(4,477)
Non-current			(105,664)	(100,910)
Accrued pension and postretirement benefits			(110,534)	(105,387)
Accumulated other comprehensive loss:
Net loss			35,177	32,514
Total accumulated other comprehensive loss			35,177	32,514
Amounts expected to be recognized from AOCI into the statement of operations in the following year:
Amortization of net loss			2,825	2,434
Total			2,825	2,434
Components of net periodic pension cost and postretirement health care benefit cost
Service cost			337	267	387
Interest cost			4,385	4,578	4,330
Amortization of prior service cost				(2,895)	(5,789)
Recognized actuarial loss			2,433	1,996	3,717
Net periodic benefit cost			$ 7,155	$ 3,946	$ 2,645
Assumptions relating to health care cost trend rates
Annual rate of increase for the costs of covered health care benefits on the basis of age (as a percent)			5.00%
Assumptions used to determine benefit obligation
Discount rate (as a percent)			4.25%	4.25%
Assumptions used to determine net periodic benefit cost
Discount rate (as a percent)			4.25%	4.75%	3.875%
Postretirement health care | Over Sixty Five Age Group
Assumptions relating to health care cost trend rates
Annual rate of increase for the costs of covered health care benefits on the basis of age (as a percent)			5.00%	5.00%
Postretirement health care | Under Sixty Five Age Group
Assumptions relating to health care cost trend rates
Annual rate of increase for the costs of covered health care benefits on the basis of age (as a percent)			5.00%	5.50%
Non Qualified Pension Plans Defined Benefit
Accrued pension and postretirement benefits:
Current			$ (95)	$ (95)
Non-current			(763)	(718)
Accrued pension and postretirement benefits			(858)	(813)
Components of net periodic pension cost and postretirement health care benefit cost
Net periodic benefit cost			$ 140	$ 84	$ 12