CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Common stock issuance cost	$ 1	$ 2	$ 2
Common stock, par value	$ 0.01	$ 0.01	$ 0.01
Common stock, authorized (in shares)	800,000,000	800,000,000	800,000,000
Common stock, outstanding (in shares)	416,000,000	421,000,000
Comprehensive income	$ 1,603	$ 1,954	$ 1,802
Outstanding and unallocated shares held by the Employee Stock Ownership Plan (ESOP) Trust (in shares)	4,000,000	5,000,000	6,000,000
Original number of shares purchased and held by the ESOP Trust (in shares)	25,000,000