Long-Term Debt (Debt Redemptions) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended	1 Months Ended
	Dec. 31, 2013	Sep. 30, 2013 Securitization Bonds [Member]	Mar. 31, 2013 Securitization Bonds [Member]	Dec. 31, 2013 Tax Exempt Revenue Bonds [Member]	Mar. 31, 2013 Tax Exempt Revenue Bonds [Member]	Apr. 30, 2013 Long Term Debt, Other [Member]	Sep. 30, 2013 Senior Notes [Member]	Dec. 31, 2013 Tax-Exempt Revenue Bonds 1 [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.62%	6.42%	5.50%	5.30%		6.40%	6.75%
Extinguishment of Debt, Amount	$ 590	$ 89	$ 88	$ 49	$ 51	$ 13	$ 250	$ 50