Consolidated Balance Sheet (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Consolidated Balance Sheet [Abstract]
Held-to-maturity, fair value	$ 35,081	$ 19,216
Held-to-maturity, pledged as collateral	833	155
Available-for-sale securities, pledged as collateral	5,876	6,831
Mortgage loans, carried at fair value	8,223	6,925
Time deposit	$ 100,000	$ 100,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized (actual number of shares)	4,000,000,000	4,000,000,000
Common stock, shares issued (actual number of shares)	2,125,725,742	2,125,725,742
Treasury stock, shares (actual number of shares)	234,207,352	215,904,019