Other Non-Operating Expense (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2012	Mar. 31, 2012 MW	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Component of Other Expense, Nonoperating [Line Items]
Other non-operating expense	$ 0		$ 82	$ 50	$ 82
Innovent [Member]
Component of Other Expense, Nonoperating [Line Items]
Other non-operating expense	0	17	0	17	0
Generation Capacity (MW)		75
Fair Value		19
Carrying Amount		36
Other Nonoperating Other [Member]
Component of Other Expense, Nonoperating [Line Items]
Other non-operating expense	0		3	1	3
China Generation [Member]
Component of Other Expense, Nonoperating [Line Items]
Other non-operating expense	0	32	79	32	79
Fair Value		133
Carrying Amount		$ 165