Securities - Amortized Cost, Fair Value, by Contract Maturity (Details 6) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, maturities, due in 1 year or less, amortized cost	$ 34,987
Available-for-sale securities, maturities, due after 1 year through 5 years, amortized cost	62,287
Available-for-sale securities, maturities, due after 5 years through 10 years, amortized cost	62,089
Available-for-sale securities, maturities, due after 10 years, amortized cost	200,529
Available-for-sale securities, maturities, amortized cost, total	359,892		358,940
Available-for-sale securities, maturities, due in 1 year or less, fair value	35,033
Available-for-sale securities, maturities, due after 1 year through 5 years, fair value	63,400
Available-for-sale securities, maturities, due after 5 years through 10 years, fair value	63,646
Available-for-sale securities, maturities, due after 10 years, fair value	209,066
Available-for-sale securities, maturities, fair value, total	364,781	371,145
Available-for-sale securities, maturities, average yield, due in 1 year or less	1.57%
Available-for-sale securities, maturities, average yield, due after 1 year through 5 years	2.17%
Available-for-sale securities, maturities, average yield, due after 5 years through 10 years	1.94%
Available-for-sale securities, maturities, average yield, due after 10 years	3.25%
Available-for-sale securities, maturities, average yield, total	2.67%
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	7
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	8
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	6.83%
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%
Non Agency Residential Collateralized Mortgage Obligations Estimated Duration	4 years
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
Debt Securities [Member]
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, due in 1 year or less, amortized cost	34,987	34,987
Available-for-sale securities, due after 1 year through 5 years, amortized cost	62,287	62,287
Available-for-sale securities, due after 5 years through 10 years, amortized cost	62,089	62,089
Available-for-sale securities, due after 10 years, amortized cost	197,779	197,779
Available-for-sale Securities, Debt Maturities, Amortized Cost	357,142	357,142
Available-for-sale securities, due in 1 year or less, fair value	35,033	35,033
Available-for-sale securities, due after 1 year through 5 years, fair value	63,400	63,400
Available-for-sale securities, due after 5 years through 10 years, fair value	63,646	63,646
Available-for-sale securities, due after 10 years, fair value	206,295	206,295
Available-for-sale securities, fair value, total	368,374	368,374
Available-for-sale securities, average yield, due in 1 year or less	1.57%	1.57%
Available-for-sale securities, average yield, due after 1 year through 5 years	2.17%	2.17%
Available-for-sale securities, average yield, due after 5 years through 10 years	1.94%	1.94%
Available-for-sale securities, average yield, due after 10 years	3.29%	3.29%
Available-for-sale securities, average yield, total	2.69%	2.69%
Available-for-sale securities, maturities, amortized cost, total	357,142	357,142	356,247
Available-for-sale securities, maturities, fair value, total		368,374	362,076
Mortgage-backed securities [Member]
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, due in 1 year or less, amortized cost	102	102
Available-for-sale securities, due after 1 year through 5 years, amortized cost	11,915	11,915
Available-for-sale securities, due after 5 years through 10 years, amortized cost	10,568	10,568
Available-for-sale securities, due after 10 years, amortized cost	156,412	156,412
Available-for-sale Securities, Debt Maturities, Amortized Cost	178,997	178,997
Available-for-sale securities, due in 1 year or less, fair value	103	103
Available-for-sale securities, due after 1 year through 5 years, fair value	12,268	12,268
Available-for-sale securities, due after 5 years through 10 years, fair value	11,008	11,008
Available-for-sale securities, due after 10 years, fair value	162,851	162,851
Available-for-sale securities, fair value, total	186,230	186,230
Available-for-sale securities, average yield, due in 1 year or less	1.91%	1.91%
Available-for-sale securities, average yield, due after 1 year through 5 years	1.94%	1.94%
Available-for-sale securities, average yield, due after 5 years through 10 years	2.81%	2.81%
Available-for-sale securities, average yield, due after 10 years	3.15%	3.15%
Available-for-sale securities, average yield, total	3.05%	3.05%
Available-for-sale securities, maturities, amortized cost, total	178,997	178,997	180,838
Available-for-sale securities, maturities, fair value, total		186,230	185,893
U.S. Treasury and government agencies [Member]
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, due in 1 year or less, amortized cost	7,779	7,779
Available-for-sale securities, due after 1 year through 5 years, amortized cost	1,502	1,502
Available-for-sale securities, due after 5 years through 10 years, amortized cost	1,651	1,651
Available-for-sale securities, due after 10 years, amortized cost	1,090	1,090
Available-for-sale Securities, Debt Maturities, Amortized Cost	12,022	12,022
Available-for-sale securities, due in 1 year or less, fair value	7,805	7,805
Available-for-sale securities, due after 1 year through 5 years, fair value	1,558	1,558
Available-for-sale securities, due after 5 years through 10 years, fair value	1,653	1,653
Available-for-sale securities, due after 10 years, fair value	1,114	1,114
Available-for-sale securities, fair value, total	12,130	12,130
Available-for-sale securities, average yield, due in 1 year or less	0.51%	0.51%
Available-for-sale securities, average yield, due after 1 year through 5 years	2.29%	2.29%
Available-for-sale securities, average yield, due after 5 years through 10 years	1.17%	1.17%
Available-for-sale securities, average yield, due after 10 years	0.78%	0.78%
Available-for-sale securities, average yield, total	0.85%	0.85%
Available-for-sale securities, maturities, amortized cost, total	12,022	12,022	8,184
Available-for-sale securities, maturities, fair value, total		12,130	8,351
Obligations of U.S. states and municipalities [Member]
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, due in 1 year or less, amortized cost	23	23
Available-for-sale securities, due after 1 year through 5 years, amortized cost	436	436
Available-for-sale securities, due after 5 years through 10 years, amortized cost	972	972
Available-for-sale securities, due after 10 years, amortized cost	18,445	18,445
Available-for-sale Securities, Debt Maturities, Amortized Cost	19,876	19,876
Available-for-sale securities, due in 1 year or less, fair value	23	23
Available-for-sale securities, due after 1 year through 5 years, fair value	471	471
Available-for-sale securities, due after 5 years through 10 years, fair value	1,033	1,033
Available-for-sale securities, due after 10 years, fair value	20,184	20,184
Available-for-sale securities, fair value, total	21,711	21,711
Available-for-sale securities, average yield, due in 1 year or less	3.45%	3.45%
Available-for-sale securities, average yield, due after 1 year through 5 years	5.52%	5.52%
Available-for-sale securities, average yield, due after 5 years through 10 years	4.08%	4.08%
Available-for-sale securities, average yield, due after 10 years	6.02%	6.02%
Available-for-sale securities, average yield, total	5.91%	5.91%
Available-for-sale securities, maturities, amortized cost, total	19,876	19,876	15,404
Available-for-sale securities, maturities, fair value, total		21,711	16,540
Certificates of Deposit [Member]
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, due in 1 year or less, amortized cost	2,730	2,730
Available-for-sale securities, due after 1 year through 5 years, amortized cost	51	51
Available-for-sale securities, due after 5 years through 10 years, amortized cost	0	0
Available-for-sale securities, due after 10 years, amortized cost	0	0
Available-for-sale Securities, Debt Maturities, Amortized Cost	2,781	2,781
Available-for-sale securities, due in 1 year or less, fair value	2,729	2,729
Available-for-sale securities, due after 1 year through 5 years, fair value	54	54
Available-for-sale securities, due after 5 years through 10 years, fair value	0	0
Available-for-sale securities, due after 10 years, fair value	0	0
Available-for-sale securities, fair value, total	2,783	2,783
Available-for-sale securities, average yield, due in 1 year or less	5.78%	5.78%
Available-for-sale securities, average yield, due after 1 year through 5 years	3.28%	3.28%
Available-for-sale securities, average yield, due after 5 years through 10 years	0.00%	0.00%
Available-for-sale securities, average yield, due after 10 years	0.00%	0.00%
Available-for-sale securities, average yield, total	5.73%	5.73%
Available-for-sale securities, maturities, amortized cost, total	2,781	2,781	3,017
Available-for-sale securities, maturities, fair value, total		2,783	3,017
Non-U.S. government debt securities [Member]
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, due in 1 year or less, amortized cost	18,248	18,248
Available-for-sale securities, due after 1 year through 5 years, amortized cost	21,937	21,937
Available-for-sale securities, due after 5 years through 10 years, amortized cost	22,870	22,870
Available-for-sale securities, due after 10 years, amortized cost	2,113	2,113
Available-for-sale Securities, Debt Maturities, Amortized Cost	65,168	65,168
Available-for-sale securities, due in 1 year or less, fair value	18,254	18,254
Available-for-sale securities, due after 1 year through 5 years, fair value	22,172	22,172
Available-for-sale securities, due after 5 years through 10 years, fair value	23,386	23,386
Available-for-sale securities, due after 10 years, fair value	2,232	2,232
Available-for-sale securities, fair value, total	66,044	66,044
Available-for-sale securities, average yield, due in 1 year or less	1.23%	1.23%
Available-for-sale securities, average yield, due after 1 year through 5 years	2.03%	2.03%
Available-for-sale securities, average yield, due after 5 years through 10 years	1.40%	1.40%
Available-for-sale securities, average yield, due after 10 years	1.65%	1.65%
Available-for-sale securities, average yield, total	1.57%	1.57%
Available-for-sale securities, maturities, amortized cost, total	65,168	65,168	44,944
Available-for-sale securities, maturities, fair value, total		66,044	45,265
Corporate Debt Securities [Member]
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, due in 1 year or less, amortized cost	5,605	5,605
Available-for-sale securities, due after 1 year through 5 years, amortized cost	23,342	23,342
Available-for-sale securities, due after 5 years through 10 years, amortized cost	8,899	8,899
Available-for-sale securities, due after 10 years, amortized cost	153	153
Available-for-sale Securities, Debt Maturities, Amortized Cost	37,999	37,999
Available-for-sale securities, due in 1 year or less, fair value	5,618	5,618
Available-for-sale securities, due after 1 year through 5 years, fair value	23,732	23,732
Available-for-sale securities, due after 5 years through 10 years, fair value	9,098	9,098
Available-for-sale securities, due after 10 years, fair value	161	161
Available-for-sale securities, fair value, total	38,609	38,609
Available-for-sale securities, average yield, due in 1 year or less	2.09%	2.09%
Available-for-sale securities, average yield, due after 1 year through 5 years	2.37%	2.37%
Available-for-sale securities, average yield, due after 5 years through 10 years	2.57%	2.57%
Available-for-sale securities, average yield, due after 10 years	3.99%	3.99%
Available-for-sale securities, average yield, total	2.38%	2.38%
Available-for-sale securities, maturities, amortized cost, total	37,999	37,999	63,607
Available-for-sale securities, maturities, fair value, total		38,609	62,176
Asset-backed Securities [Member]
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, due in 1 year or less, amortized cost	500	500
Available-for-sale securities, due after 1 year through 5 years, amortized cost	3,104	3,104
Available-for-sale securities, due after 5 years through 10 years, amortized cost	17,129	17,129
Available-for-sale securities, due after 10 years, amortized cost	19,566	19,566
Available-for-sale Securities, Debt Maturities, Amortized Cost	40,299	40,299
Available-for-sale securities, due in 1 year or less, fair value	501	501
Available-for-sale securities, due after 1 year through 5 years, fair value	3,145	3,145
Available-for-sale securities, due after 5 years through 10 years, fair value	17,468	17,468
Available-for-sale securities, due after 10 years, fair value	19,753	19,753
Available-for-sale securities, fair value, total	40,867	40,867
Available-for-sale securities, average yield, due in 1 year or less	1.08%	1.08%
Available-for-sale securities, average yield, due after 1 year through 5 years	2.10%	2.10%
Available-for-sale securities, average yield, due after 5 years through 10 years	1.75%	1.75%
Available-for-sale securities, average yield, due after 10 years	2.09%	2.09%
Available-for-sale securities, average yield, total	1.93%	1.93%
Equity securities [Member]
Amortized cost and estimated fair value by contractual maturity
Available-for-sale securities, equity maturities, due in 1 year or less, amortized cost	0	0
Available-for-sale securities, equity maturities, due after 1 year through 5 years, amortized cost	0	0
Available-for-sale securities, equity maturities, due after 5 years through 10 years, amortized cost	0	0
Available-for-sale securities, equity maturities, due after 10 years, amortized cost	2,750	2,750
Available-for-sale securities, equity maturities, amortized cost, total	2,750	2,750
Available-for-sale securities, equity maturities, due in 1 year or less, fair value	0	0
Available-for-sale securities, equity maturities, due after 1 year through 5 years, fair value	0	0
Available-for-sale securities, equity maturities, due after 5 years through 10 years, fair value	0	0
Available-for-sale securities, equity maturities, due after 10 years, fair value	2,771	2,771
Available-for-sale securities, equity maturities, fair value, total	2,771	2,771
Available-for-sale securities, equity maturities, average yield, due in 1 year or less	0.00%	0.00%
Available-for-sale securities, equity maturities, average yield, due after 1 year through 5 years	0.00%	0.00%
Available-for-sale securities, equity maturities, average yield, due after 5 years through 10 years	0.00%	0.00%
Available-for-sale securities, equity maturities, average yield, due after 10 years	0.36%	0.36%
Available-for-sale securities, equity maturities, average yield, total	0.36%	0.36%
Available-for-sale securities, maturities, amortized cost, total	2,750	2,750	2,693
Available-for-sale securities, maturities, fair value, total		$ 2,771	$ 2,705
Minimum [Member]
Supplemental information
Due Period Of Mortgage Backed Securities And Collateralized Mortgage Obligations	10 years