Investments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net unrealized gains and losses on trading securities		$ 5	$ 11
Equity earnings on investments	35	42	42
Company received distribution from Fowler Ridge in connection with non-recourse permanent financing	43	47	174
Carrying amount of Company's investments exceeded its shares of underlying equity	32	7
Restricted cash and cash equivalent for funding qualifying projects	147	415
Categories of Investments, Marketable Securities, Trading Securities [Member]
Investments held in our rabbi trusts	90	93
Categories of Investments, Cost-method Investments [Member]
Investments held in our rabbi trusts	17	18
Fowler I Holdings LLC [Member]
Company received distribution from Fowler Ridge in connection with non-recourse permanent financing			123
Dominion [Member]
Company received distribution from Fowler Ridge in connection with non-recourse permanent financing	55	60	63
Maximum [Member]
Net unrealized gains and losses on trading securities	$ 1