Retirement and Post-Retirement Employee Benefit Plans Net Periodic Cost (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Pension Plans Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 15,084	$ 14,384	$ 13,499
Interest cost	21,568	22,264	20,870
Expected return on assets	21,474	24,817	25,280
Amortization of prior service cost	(141)	(429)	(960)
Recognized actuarial loss	(14,451)	(9,498)	(9,290)
Curtailment loss	0	40	0
Net periodic cost	29,488	20,860	17,419
Other Postretirement Benefit Plans Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	16,353	14,403	13,439
Interest cost	13,861	12,813	12,071
Expected return on assets	2,607	2,727	2,460
Amortization of transition asset	1,511	1,511	1,511
Amortization of prior service cost	(1,450)	(1,450)	(1,450)
Recognized actuarial loss	(2,648)	(347)	(374)
Net periodic cost	30,316	24,897	23,485
Supplemental Executive Retirement Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2,108	2,768	2,476
Interest cost	5,142	5,825	5,224
Amortization of transition asset	0	0	0
Amortization of prior service cost	0	0	187
Recognized actuarial loss	(2,118)	(2,239)	(1,999)
Net periodic cost	$ 9,368	$ 10,832	$ 9,886