Securities - Amortized Cost, Fair Value, by Contract Maturity (Details 6) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, maturities, due in 1 year or less, amortized cost	$ 31,275
Available-for-sale securities, maturities, due after 1 year through 5 years, amortized cost	60,943
Available-for-sale securities, maturities, due after 5 years through 10 years, amortized cost	61,890
Available-for-sale securities, maturities, due after 10 years, amortized cost	201,401
Available-for-sale securities, maturities, amortized cost, total	355,509	359,892
Available-for-sale securities, maturities, due in 1 year or less, fair value	31,355
Available-for-sale securities, maturities, due after 1 year through 5 years, fair value	62,153
Available-for-sale securities, maturities, due after 5 years through 10 years, fair value	63,424
Available-for-sale securities, maturities, due after 10 years, fair value	208,805
Available-for-sale Securities	365,737	371,145
Available-for-sale securities, maturities, average yield, due in 1 year or less	1.58%
Available-for-sale securities, maturities, average yield, due after 1 year through 5 years	2.16%
Available-for-sale securities, maturities, average yield, due after 5 years through 10 years	2.00%
Available-for-sale securities, maturities, average yield, due after 10 years	3.26%
Available-for-sale securities, maturities, average yield, total	2.70%
Held-to-maturity securities, maturities, due in 1 year or less, amortized cost	0
Held-to-maturity securities, maturities, due after 1 year through 5 years, amortized cost	6
Held-to-maturity securities, maturities, due after 5 years through 10 years, amortized cost	1
Held-to-maturity securities, maturities, due after 10 years, amortized cost	0
Held-to-maturity securities, maturities, amortized cost, total	7
Held-to-maturity securities, maturities, due in 1 year or less, fair value	0
Held-to-maturity securities, maturities, due after 1 year through 5 years, fair value	6
Held-to-maturity securities, maturities, due after 5 years through 10 years, fair value	1
Held-to-maturity securities, maturities, due after 10 years, fair value	0
Held-to-maturity securities, maturities, fair value, total	7
Held-to-maturity securities, maturities, average yield, due in 1 year or less	0.00%
Held-to-maturity securities, maturities, average yield, due after 1 year through 5 years	6.85%
Held-to-maturity securities, maturities, average yield, due after 5 years through 10 years	6.64%
Held-to-maturity securities, maturities, average yield, due after 10 years	0.00%
Held-to-maturity securities, maturities, average yield, total	6.84%
Supplemental information
U S Government And Government Agencies And Authorities And U S Government Sponsored Enterprise Securities In Excess Of Ten Percent Of Stockholders Equity	10.00%
US Government Agencies And US Government sponsored Enterprises Residential Mortgage Backed Securities Estimated Duration	3 years
US Government Agencies And US Government-sponsored Enterprises, Residential Collateralized Mortgage Obligations, Estimated Duration	2 years
Non Agency Residential Collateralized Mortgage Obligations Estimated Duration	3 years
Minimum
Supplemental information
Due Period Of Mortgage Backed Securities And Collateralized Mortgage Obligations	10 years
Equity securities
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, equity maturities, due in 1 year or less, amortized cost	0
Available-for-sale securities, equity maturities, due after 1 year through 5 years, amortized cost	0
Available-for-sale securities, equity maturities, due after 5 years through 10 years, amortized cost	0
Available-for-sale securities, equity maturities, due after 10 years, amortized cost	2,458
Available-for-sale securities, equity maturities, amortized cost, total	2,458
Available-for-sale securities, equity maturities, due in 1 year or less, fair value	0
Available-for-sale securities, equity maturities, due after 1 year through 5 years, fair value	0
Available-for-sale securities, equity maturities, due after 5 years through 10 years, fair value	0
Available-for-sale securities, equity maturities, due after 10 years, fair value	2,474
Available-for-sale securities, equity maturities, fair value, total	2,474
Available-for-sale securities, equity maturities, average yield, due in 1 year or less	0.00%
Available-for-sale securities, equity maturities, average yield, due after 1 year through 5 years	0.00%
Available-for-sale securities, equity maturities, average yield, due after 5 years through 10 years	0.00%
Available-for-sale securities, equity maturities, average yield, due after 10 years	0.18%
Available-for-sale securities, equity maturities, average yield, total	0.18%
Available-for-sale securities, maturities, amortized cost, total	2,458	2,750
Available-for-sale Securities	2,474	2,771
Debt Securities
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, due in 1 year or less, amortized cost	31,275
Available-for-sale securities, due after 1 year through 5 years, amortized cost	60,943
Available-for-sale securities, due after 5 years through 10 years, amortized cost	61,890
Available-for-sale securities, due after 10 years, amortized cost	198,943
Available-for-sale Securities, Debt Maturities, Amortized Cost	353,051
Available-for-sale securities, due in 1 year or less, fair value	31,355
Available-for-sale securities, due after 1 year through 5 years, fair value	62,153
Available-for-sale securities, due after 5 years through 10 years, fair value	63,424
Available-for-sale securities, due after 10 years, fair value	206,331
Available-for-sale securities, fair value, total	363,263
Available-for-sale securities, average yield, due in 1 year or less	1.58%
Available-for-sale securities, average yield, due after 1 year through 5 years	2.16%
Available-for-sale securities, average yield, due after 5 years through 10 years	2.00%
Available-for-sale securities, average yield, due after 10 years	3.29%
Available-for-sale securities, average yield, total	2.72%
Available-for-sale securities, maturities, amortized cost, total	353,051	357,142
Available-for-sale Securities	363,263	368,374
Mortgage-backed securities
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, due in 1 year or less, amortized cost	142
Available-for-sale securities, due after 1 year through 5 years, amortized cost	13,090
Available-for-sale securities, due after 5 years through 10 years, amortized cost	11,304
Available-for-sale securities, due after 10 years, amortized cost	153,911
Available-for-sale Securities, Debt Maturities, Amortized Cost	178,447
Available-for-sale securities, due in 1 year or less, fair value	142
Available-for-sale securities, due after 1 year through 5 years, fair value	13,542
Available-for-sale securities, due after 5 years through 10 years, fair value	11,798
Available-for-sale securities, due after 10 years, fair value	159,355
Available-for-sale securities, fair value, total	184,837
Available-for-sale securities, average yield, due in 1 year or less	2.40%
Available-for-sale securities, average yield, due after 1 year through 5 years	1.98%
Available-for-sale securities, average yield, due after 5 years through 10 years	3.19%
Available-for-sale securities, average yield, due after 10 years	3.24%
Available-for-sale securities, average yield, total	3.15%
Available-for-sale securities, maturities, amortized cost, total	178,447	178,997
Available-for-sale Securities	184,837	186,230
U.S. Treasury and government agencies
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, due in 1 year or less, amortized cost	6,133
Available-for-sale securities, due after 1 year through 5 years, amortized cost	1,804
Available-for-sale securities, due after 5 years through 10 years, amortized cost	2,832
Available-for-sale securities, due after 10 years, amortized cost	1,035
Available-for-sale Securities, Debt Maturities, Amortized Cost	11,804
Available-for-sale securities, due in 1 year or less, fair value	6,152
Available-for-sale securities, due after 1 year through 5 years, fair value	1,854
Available-for-sale securities, due after 5 years through 10 years, fair value	2,853
Available-for-sale securities, due after 10 years, fair value	1,071
Available-for-sale securities, fair value, total	11,930
Available-for-sale securities, average yield, due in 1 year or less	0.57%
Available-for-sale securities, average yield, due after 1 year through 5 years	1.91%
Available-for-sale securities, average yield, due after 5 years through 10 years	0.75%
Available-for-sale securities, average yield, due after 10 years	0.72%
Available-for-sale securities, average yield, total	0.83%
Available-for-sale securities, maturities, amortized cost, total	11,804	12,022
Available-for-sale Securities	11,930	12,130
Obligations of U.S. states and municipalities
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, due in 1 year or less, amortized cost	23
Available-for-sale securities, due after 1 year through 5 years, amortized cost	435
Available-for-sale securities, due after 5 years through 10 years, amortized cost	1,088
Available-for-sale securities, due after 10 years, amortized cost	17,855
Available-for-sale Securities, Debt Maturities, Amortized Cost	19,401
Available-for-sale securities, due in 1 year or less, fair value	23
Available-for-sale securities, due after 1 year through 5 years, fair value	470
Available-for-sale securities, due after 5 years through 10 years, fair value	1,161
Available-for-sale securities, due after 10 years, fair value	19,324
Available-for-sale securities, fair value, total	20,978
Available-for-sale securities, average yield, due in 1 year or less	3.35%
Available-for-sale securities, average yield, due after 1 year through 5 years	5.43%
Available-for-sale securities, average yield, due after 5 years through 10 years	3.69%
Available-for-sale securities, average yield, due after 10 years	5.85%
Available-for-sale securities, average yield, total	5.72%
Available-for-sale securities, maturities, amortized cost, total	19,401	19,876
Available-for-sale Securities	20,978	21,711
Certificates of Deposit
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, due in 1 year or less, amortized cost	2,322
Available-for-sale securities, due after 1 year through 5 years, amortized cost	51
Available-for-sale securities, due after 5 years through 10 years, amortized cost	0
Available-for-sale securities, due after 10 years, amortized cost	0
Available-for-sale Securities, Debt Maturities, Amortized Cost	2,373
Available-for-sale securities, due in 1 year or less, fair value	2,325
Available-for-sale securities, due after 1 year through 5 years, fair value	54
Available-for-sale securities, due after 5 years through 10 years, fair value	0
Available-for-sale securities, due after 10 years, fair value	0
Available-for-sale securities, fair value, total	2,379
Available-for-sale securities, average yield, due in 1 year or less	6.23%
Available-for-sale securities, average yield, due after 1 year through 5 years	3.28%
Available-for-sale securities, average yield, due after 5 years through 10 years	0.00%
Available-for-sale securities, average yield, due after 10 years	0.00%
Available-for-sale securities, average yield, total	6.17%
Available-for-sale securities, maturities, amortized cost, total	2,373	2,781
Available-for-sale Securities	2,379	2,783
Non-U.S. government debt securities
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, due in 1 year or less, amortized cost	18,728
Available-for-sale securities, due after 1 year through 5 years, amortized cost	21,971
Available-for-sale securities, due after 5 years through 10 years, amortized cost	26,319
Available-for-sale securities, due after 10 years, amortized cost	2,427
Available-for-sale Securities, Debt Maturities, Amortized Cost	69,445
Available-for-sale securities, due in 1 year or less, fair value	18,771
Available-for-sale securities, due after 1 year through 5 years, fair value	22,209
Available-for-sale securities, due after 5 years through 10 years, fair value	26,844
Available-for-sale securities, due after 10 years, fair value	2,543
Available-for-sale securities, fair value, total	70,367
Available-for-sale securities, average yield, due in 1 year or less	1.09%
Available-for-sale securities, average yield, due after 1 year through 5 years	2.13%
Available-for-sale securities, average yield, due after 5 years through 10 years	1.46%
Available-for-sale securities, average yield, due after 10 years	1.77%
Available-for-sale securities, average yield, total	1.58%
Available-for-sale securities, maturities, amortized cost, total	69,445	65,168
Available-for-sale Securities	70,367	66,044
Corporate Debt Securities
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, due in 1 year or less, amortized cost	3,927
Available-for-sale securities, due after 1 year through 5 years, amortized cost	20,617
Available-for-sale securities, due after 5 years through 10 years, amortized cost	7,936
Available-for-sale securities, due after 10 years, amortized cost	136
Available-for-sale Securities, Debt Maturities, Amortized Cost	32,616
Available-for-sale securities, due in 1 year or less, fair value	3,942
Available-for-sale securities, due after 1 year through 5 years, fair value	21,016
Available-for-sale securities, due after 5 years through 10 years, fair value	8,147
Available-for-sale securities, due after 10 years, fair value	134
Available-for-sale securities, fair value, total	33,239
Available-for-sale securities, average yield, due in 1 year or less	2.73%
Available-for-sale securities, average yield, due after 1 year through 5 years	2.30%
Available-for-sale securities, average yield, due after 5 years through 10 years	2.54%
Available-for-sale securities, average yield, due after 10 years	2.87%
Available-for-sale securities, average yield, total	2.41%
Available-for-sale securities, maturities, amortized cost, total	32,616	37,999
Available-for-sale Securities	33,239	38,609
Asset-backed securities
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, due in 1 year or less, amortized cost	0
Available-for-sale securities, due after 1 year through 5 years, amortized cost	2,975
Available-for-sale securities, due after 5 years through 10 years, amortized cost	12,411
Available-for-sale securities, due after 10 years, amortized cost	23,579
Available-for-sale Securities, Debt Maturities, Amortized Cost	38,965
Available-for-sale securities, due in 1 year or less, fair value	0
Available-for-sale securities, due after 1 year through 5 years, fair value	3,008
Available-for-sale securities, due after 5 years through 10 years, fair value	12,621
Available-for-sale securities, due after 10 years, fair value	23,904
Available-for-sale securities, fair value, total	$ 39,533
Available-for-sale securities, average yield, due in 1 year or less	0.00%
Available-for-sale securities, average yield, due after 1 year through 5 years	1.92%
Available-for-sale securities, average yield, due after 5 years through 10 years	1.85%
Available-for-sale securities, average yield, due after 10 years	1.95%
Available-for-sale securities, average yield, total	1.92%