Goodwill (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
Goodwill [Line Items]
Balance at beginning of period	$ 4,114
Effect of foreign currency exchange rates	47
Balance at end of period	4,161
Kentucky Regulated [Member]
Goodwill [Line Items]
Balance at beginning of period	662	[1]
Effect of foreign currency exchange rates	0
Balance at end of period	662	[1]
UK Regulated [Member]
Goodwill [Line Items]
Balance at beginning of period	3,032	[1]
Effect of foreign currency exchange rates	47
Balance at end of period	3,079	[1]
Supply [Member]
Goodwill [Line Items]
Balance at beginning of period	420	[1]
Effect of foreign currency exchange rates	0
Balance at end of period	$ 420	[1]

[1] There were no accumulated impairment losses related to goodwill.