Interim Pension and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Pension Benefits [Member]
Components of net periodic pension cost [Abstract]
Service Cost	$ 4,697	$ 5,051	$ 9,395	$ 10,102
Interest Cost	7,094	6,698	14,189	13,397
Expected return on assets	(6,880)	(6,437)	(13,761)	(12,873)
Amortization of transition (asset)/obligation	0	0	0	0
Amortization of prior service (credit)/cost	(56)	(47)	(113)	(96)
Amortization of actuarial (gain) loss	3,320	3,916	6,640	7,833
Net periodic pension cost	$ 8,175	$ 9,181	$ 16,350	$ 18,363
Defined Benefit Plan Weighted Average Assumptions Used In Calculating Net Periodic Benefit Cost Abstract
Discount Rate	4.55%	4.43%	4.55%	4.43%
Rate of compensation increase	3.50%	3.50%	3.50%	3.50%
Expected return on plan assets	7.00%	7.25%	7.00%	7.25%
Other Benefits [Member]
Components of net periodic pension cost [Abstract]
Service Cost	$ 2,706	$ 3,896	$ 5,412	$ 7,792
Interest Cost	3,106	3,597	6,212	7,193
Expected return on assets	(1,566)	(1,608)	(3,132)	(3,216)
Amortization of transition (asset)/obligation	20	68	41	136
Amortization of prior service (credit)/cost	(411)	(411)	(822)	(822)
Amortization of actuarial (gain) loss	(542)	0	(1,084)	0
Net periodic pension cost	$ 3,313	$ 5,542	$ 6,627	$ 11,083
Defined Benefit Plan Weighted Average Assumptions Used In Calculating Net Periodic Benefit Cost Abstract
Discount Rate	4.55%	4.43%	4.55%	4.43%
Expected return on plan assets	4.45%	4.60%	4.45%	4.60%
Current Year Benefit Plan Contributions [Abstract]
Contributions Actual			$ 9,000
Other Benefits [Member] | Minimum [Member]
Current Year Benefit Plan Contributions [Abstract]
Defined Benefit Plan, Expected Contributions in Current Fiscal Year			15,000
Other Benefits [Member] | Maximum [Member]
Current Year Benefit Plan Contributions [Abstract]
Defined Benefit Plan, Expected Contributions in Current Fiscal Year			$ 25,000