Consolidated Balance Sheet (Parenthetical) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Held-to-maturity securities, fair value	$ 35,226,000,000	$ 19,216,000,000
Held-to-maturity securities, pledged as collateral	1,146,000,000	155,000,000
Available-for-sale securities, pledged as collateral	2,217,000,000	6,831,000,000
Mortgage loans, carried at fair value	9,815,000,000	6,925,000,000
Time deposits	$ 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)	245,650,205	215,904,019