Consolidated Balance Sheet (Unaudited) (Parenthetical) - USD ($)	Sep. 30, 2015	Dec. 31, 2014
Held-to-maturity securities, fair value	$ 45,051,000,000	$ 45,140,000,000
Securities, pledged as collateral	1,100,000,000	856,000,000
Mortgage loans, carried at fair value	4,429,000,000	4,774,000,000
Time deposits	$ 100,000	$ 100,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, share-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)	372,131,113	339,859,034
Time deposits greater than 250,000	$ 3,500,000,000	$ 5,000,000,000
Held-to-maturity Securities [Member]
Securities, pledged as collateral	788,000,000	526,000,000
Available-for-Sale Securities [Member]
Securities, pledged as collateral	320,000,000	330,000,000
Trading Securities [Member]
Securities, pledged as collateral	$ 59,000,000	$ 157,000,000