Debt (Details 1) (USD $) In Thousands	Sep. 30, 2011	Sep. 30, 2010
Summary of Long-Term Debt
Long-term Debt, Gross	$ 2,484,665	$ 1,495,357
Domestic notes due through 2013 (average year-end interest rate: 1.05% - 2011; 1.0% - 2010) [Member]
Summary of Long-Term Debt
Long-term Debt, Gross	8,030	8,058
4.55% Notes due April 15, 2013 [Member]
Summary of Long-Term Debt
Long-term Debt, Gross	205,581	207,992
4.90% Notes due April 15, 2018 [Member]
Summary of Long-Term Debt
Long-term Debt, Gross	204,164	204,710
5.00% Notes due May 15, 2019 [Member]
Summary of Long-Term Debt
Long-term Debt, Gross	494,743	494,196
3.25% Notes due November 12, 2020 [Member]
Summary of Long-Term Debt
Long-term Debt, Gross	695,461	0
7.00% Debentures due August 1, 2027 [Member]
Summary of Long-Term Debt
Long-term Debt, Gross	168,000	168,000
6.70% Debentures due August 1, 2028 [Member]
Summary of Long-Term Debt
Long-term Debt, Gross	167,050	167,050
6.00% Notes due May 15, 2039 [Member]
Summary of Long-Term Debt
Long-term Debt, Gross	245,413	245,351
5.00% Notes due November 12, 2040 [Member]
Summary of Long-Term Debt
Long-term Debt, Gross	$ 296,223	$ 0