Charges and Credits (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Summary of Charges and Credit (Textual) [Abstract]
Charges pretax	$ 15	$ 34
Merger-related transaction costs [Member]
Summary of Charges and Credit (Textual) [Abstract]
Charges pretax	15	34
Charges, net	$ 13	$ 28