LONG-TERM AND SHORT-TERM DEBT (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
LONG-TERM AND SHORT-TERM DEBT
Total debt	$ 4,666	$ 4,503
Long-term debt
Current maturities of long-term debt	(31)	(337)
Unamortized discount	(13)	(14)
Total long-term debt, net	4,622	4,152
Annual amounts of long-term debt maturities
2012	280
2013	171
2014	52
2015	13
2016	12
Medium-Term Notes (unsecured)
Long-term debt
Total debt	800	950
Weighted average interest rate (as a percent)	5.69%	6.51%
Fixed rate debt hedged by variable interest rate swaps	250.0	550.0
Senior Notes (unsecured)
Long-term debt
Total debt	101	106
Weighted average interest rate (as a percent)	6.47%	6.47%
First Mortgage Bonds (secured)
Long-term debt
Total debt	2,790	2,560
Weighted average interest rate (as a percent)	5.89%	6.03%
Junior Subordinated Notes (unsecured)
Long-term debt
Total debt	150	150
Weighted average interest rate (as a percent)	7.70%	7.70%
GENCO Notes (secured)
Long-term debt
Total debt	247	262
Weighted average interest rate (as a percent)	5.86%	5.91%
Industrial and Pollution Control Bonds
Long-term debt
Total debt	194	228
Weighted average interest rate (as a percent)	4.48%	4.63%
Variable rate debt hedged by fixed rate swaps	71.4	71.4
Senior Debentures
Long-term debt
Total debt	353	206
Weighted average interest rate (as a percent)	5.92%	6.94%
Fixed rate debt hedged by variable interest rate swaps	3.2	6.4
Fair Value of Interest Rate Swaps
Long-term debt
Total debt		5
Other debt maturing during 2012 to 2027
Long-term debt
Total debt	$ 31	$ 36