Securities - Amortized Cost, Fair Value, by Contract Maturity (Details 5) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 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	$ 24,570
Available-for-sale securities, maturities, due after 1 year through 5 years, amortized cost	63,207
Available-for-sale securities, maturities, due after 5 years through 10 years, amortized cost	59,320
Available-for-sale securities, maturities, due after 10 years, amortized cost	202,465
Available-for-sale securities, maturities, amortized cost, total	349,562	359,892
Available-for-sale securities, maturities, due in 1 year or less, fair value	24,635
Available-for-sale securities, maturities, due after 1 year through 5 years, fair value	64,145
Available-for-sale securities, maturities, due after 5 years through 10 years, fair value	60,335
Available-for-sale securities, maturities, due after 10 years, fair value	205,604
Available-for-sale Securities	354,719	371,145
Available-for-sale securities, maturities, average yield, due in 1 year or less	1.93%
Available-for-sale securities, maturities, average yield, due after 1 year through 5 years	1.91%
Available-for-sale securities, maturities, average yield, due after 5 years through 10 years	1.85%
Available-for-sale securities, maturities, average yield, due after 10 years	3.27%
Available-for-sale securities, maturities, average yield, total	2.69%
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	5
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	6
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	5
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	6
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	6.84%
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	6.81%
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	5 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	2,595
Available-for-sale securities, equity maturities, amortized cost, total	2,595
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	2,610
Available-for-sale securities, equity maturities, fair value, total	2,610
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	0.25%
Available-for-sale securities, equity maturities, average yield, total	0.25%
Available-for-sale securities, maturities, amortized cost, total	2,595	2,750
Available-for-sale Securities	2,610	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	24,570
Available-for-sale securities, due after 1 year through 5 years, amortized cost	63,207
Available-for-sale securities, due after 5 years through 10 years, amortized cost	59,320
Available-for-sale securities, due after 10 years, amortized cost	199,870
Available-for-sale Securities, Debt Maturities, Amortized Cost	346,967
Available-for-sale securities, due in 1 year or less, fair value	24,635
Available-for-sale securities, due after 1 year through 5 years, fair value	64,145
Available-for-sale securities, due after 5 years through 10 years, fair value	60,335
Available-for-sale securities, due after 10 years, fair value	202,994
Available-for-sale securities, fair value, total	352,109
Available-for-sale securities, average yield, due in 1 year or less	1.93%
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	1.85%
Available-for-sale securities, average yield, due after 10 years	3.31%
Available-for-sale securities, average yield, total	2.71%
Available-for-sale securities, maturities, amortized cost, total	346,967	357,142
Available-for-sale Securities	352,109	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	293
Available-for-sale securities, due after 1 year through 5 years, amortized cost	14,218
Available-for-sale securities, due after 5 years through 10 years, amortized cost	9,652
Available-for-sale securities, due after 10 years, amortized cost	152,216
Available-for-sale Securities, Debt Maturities, Amortized Cost	176,379
Available-for-sale securities, due in 1 year or less, fair value	295
Available-for-sale securities, due after 1 year through 5 years, fair value	14,662
Available-for-sale securities, due after 5 years through 10 years, fair value	9,942
Available-for-sale securities, due after 10 years, fair value	154,963
Available-for-sale securities, fair value, total	179,862
Available-for-sale securities, average yield, due in 1 year or less	2.08%
Available-for-sale securities, average yield, due after 1 year through 5 years	2.08%
Available-for-sale securities, average yield, due after 5 years through 10 years	3.09%
Available-for-sale securities, average yield, due after 10 years	3.17%
Available-for-sale securities, average yield, total	3.07%
Available-for-sale securities, maturities, amortized cost, total	176,379	178,997
Available-for-sale Securities	179,862	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	7,432
Available-for-sale securities, due after 1 year through 5 years, amortized cost	12,497
Available-for-sale securities, due after 5 years through 10 years, amortized cost	1,931
Available-for-sale securities, due after 10 years, amortized cost	944
Available-for-sale Securities, Debt Maturities, Amortized Cost	22,804
Available-for-sale securities, due in 1 year or less, fair value	7,455
Available-for-sale securities, due after 1 year through 5 years, fair value	12,496
Available-for-sale securities, due after 5 years through 10 years, fair value	1,950
Available-for-sale securities, due after 10 years, fair value	997
Available-for-sale securities, fair value, total	22,898
Available-for-sale securities, average yield, due in 1 year or less	0.65%
Available-for-sale securities, average yield, due after 1 year through 5 years	0.41%
Available-for-sale securities, average yield, due after 5 years through 10 years	0.83%
Available-for-sale securities, average yield, due after 10 years	0.78%
Available-for-sale securities, average yield, total	0.54%
Available-for-sale securities, maturities, amortized cost, total	22,804	12,022
Available-for-sale Securities	22,898	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	32
Available-for-sale securities, due after 1 year through 5 years, amortized cost	466
Available-for-sale securities, due after 5 years through 10 years, amortized cost	1,335
Available-for-sale securities, due after 10 years, amortized cost	22,676
Available-for-sale Securities, Debt Maturities, Amortized Cost	24,509
Available-for-sale securities, due in 1 year or less, fair value	32
Available-for-sale securities, due after 1 year through 5 years, fair value	493
Available-for-sale securities, due after 5 years through 10 years, fair value	1,357
Available-for-sale securities, due after 10 years, fair value	22,651
Available-for-sale securities, fair value, total	24,533
Available-for-sale securities, average yield, due in 1 year or less	2.95%
Available-for-sale securities, average yield, due after 1 year through 5 years	5.27%
Available-for-sale securities, average yield, due after 5 years through 10 years	4.02%
Available-for-sale securities, average yield, due after 10 years	5.91%
Available-for-sale securities, average yield, total	5.79%
Available-for-sale securities, maturities, amortized cost, total	24,509	19,876
Available-for-sale Securities	24,533	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	1,531
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	1,582
Available-for-sale securities, due in 1 year or less, fair value	1,535
Available-for-sale securities, due after 1 year through 5 years, fair value	53
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	1,588
Available-for-sale securities, average yield, due in 1 year or less	7.67%
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	7.53%
Available-for-sale securities, maturities, amortized cost, total	1,582	2,781
Available-for-sale Securities	1,588	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	11,112
Available-for-sale securities, due after 1 year through 5 years, amortized cost	16,429
Available-for-sale securities, due after 5 years through 10 years, amortized cost	25,469
Available-for-sale securities, due after 10 years, amortized cost	2,204
Available-for-sale Securities, Debt Maturities, Amortized Cost	55,214
Available-for-sale securities, due in 1 year or less, fair value	11,145
Available-for-sale securities, due after 1 year through 5 years, fair value	16,616
Available-for-sale securities, due after 5 years through 10 years, fair value	25,915
Available-for-sale securities, due after 10 years, fair value	2,298
Available-for-sale securities, fair value, total	55,974
Available-for-sale securities, average yield, due in 1 year or less	1.90%
Available-for-sale securities, average yield, due after 1 year through 5 years	2.32%
Available-for-sale securities, average yield, due after 5 years through 10 years	1.20%
Available-for-sale securities, average yield, due after 10 years	1.67%
Available-for-sale securities, average yield, total	1.69%
Available-for-sale securities, maturities, amortized cost, total	55,214	65,168
Available-for-sale Securities	55,974	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	4,170
Available-for-sale securities, due after 1 year through 5 years, amortized cost	16,790
Available-for-sale securities, due after 5 years through 10 years, amortized cost	6,924
Available-for-sale securities, due after 10 years, amortized cost	53
Available-for-sale Securities, Debt Maturities, Amortized Cost	27,937
Available-for-sale securities, due in 1 year or less, fair value	4,173
Available-for-sale securities, due after 1 year through 5 years, fair value	17,042
Available-for-sale securities, due after 5 years through 10 years, fair value	6,969
Available-for-sale securities, due after 10 years, fair value	55
Available-for-sale securities, fair value, total	28,239
Available-for-sale securities, average yield, due in 1 year or less	2.19%
Available-for-sale securities, average yield, due after 1 year through 5 years	2.40%
Available-for-sale securities, average yield, due after 5 years through 10 years	2.57%
Available-for-sale securities, average yield, due after 10 years	2.34%
Available-for-sale securities, average yield, total	2.41%
Available-for-sale securities, maturities, amortized cost, total	27,937	37,999
Available-for-sale Securities	28,239	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	2,756
Available-for-sale securities, due after 5 years through 10 years, amortized cost	14,009
Available-for-sale securities, due after 10 years, amortized cost	21,777
Available-for-sale Securities, Debt Maturities, Amortized Cost	38,542
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	2,783
Available-for-sale securities, due after 5 years through 10 years, fair value	14,202
Available-for-sale securities, due after 10 years, fair value	22,030
Available-for-sale securities, fair value, total	$ 39,015
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	1.86%
Available-for-sale securities, average yield, due after 5 years through 10 years	1.76%
Available-for-sale securities, average yield, due after 10 years	1.90%
Available-for-sale securities, average yield, total	1.85%