Consolidated Balance Sheet (Unaudited) (Parenthetical) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Held-to-maturity securities, fair value	$ 40,389,000,000	$ 38,368,000,000
Securities, pledged as collateral	652,000,000	2,100,000,000
Mortgage loans, carried at fair value	1,827,000,000	3,263,000,000
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)	304,447,591	300,977,274
Held-to-maturity Securities [Member]
Securities, pledged as collateral	498,000,000	994,000,000
Available-for-Sale Securities [Member]
Securities, pledged as collateral	154,000,000	1,106,000,000
Trading Securities [Member]
Securities, pledged as collateral	$ 55,000,000	$ 111,000,000