Fair Value Measurements (Details 4) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Proceeds from the sale of investments in available-for-sale securities, realized gains and losses on those sales, and interest and dividend income
Sales Proceeds	$ 539	$ 251
Realized Gains	25	19
Realized Losses	(13)	(17)
Interest and Dividend Income	26	15
FES
Proceeds from the sale of investments in available-for-sale securities, realized gains and losses on those sales, and interest and dividend income
Sales Proceeds	252	83
Realized Gains	20	12
Realized Losses	(10)	(11)
Interest and Dividend Income	$ 13	$ 7