Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011
Pension Plans [Member]
Net pension and postretirement cost
Service cost	$ 17,723	$ 22,749	$ 40,752	$ 45,653
Interest cost	21,540	23,100	49,529	46,358
Expected return on plan assets	(24,452)	(25,384)	(56,224)	(50,941)
Amortization of prior service credit	(2,594)	(268)	(5,964)	(538)
Amortization of loss	13,234	13,786	30,430	27,667
Curtailment/settlement loss		1,083		1,083
Net pension and postretirement cost	25,451	35,066	58,523	69,282
Other Postretirement Benefits [Member]
Net pension and postretirement cost
Service cost	1,475	1,445	2,945	2,918
Interest cost	3,220	3,283	6,435	6,567
Amortization of prior service credit	(172)	(172)	(345)	(344)
Amortization of loss	1,163	1,115	2,325	2,232
Net pension and postretirement cost	$ 5,686	$ 5,671	$ 11,360	$ 11,373