Long-Term Debt (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Dec. 31, 2011
Extinguishment of Debt [Line Items]
Extinguishment of Debt, Amount	$ 1,280
Tax-Exempt Revenue Bonds 2 [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.95%
Extinguishment of Debt, Amount	26
Senior Notes 1 [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.05%
Extinguishment of Debt, Amount	600
Tax-Exempt Revenue Bonds 3 [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.55%
Extinguishment of Debt, Amount	118
Tax-Exempt Revenue Bonds 4 [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.65%
Extinguishment of Debt, Amount	67
Tax Exempt Revenue Bonds 5 [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.65%
Extinguishment of Debt, Amount	40
Tax Exempt Revenue Bonds 6 [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.45%
Extinguishment of Debt, Amount	140
Trust preferred-linked securities [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.80%
Extinguishment of Debt, Amount	186
Trust preferred-linked securities 1 [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.50%
Extinguishment of Debt, Amount	$ 103