Investment Securities (Contractual Maturity of Debt Securities) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Total	$ 47,176	$ 49,447
Available-for-sale Securities, Fair value	47,899	51,052
Weighted-average yield, GAAP basis, available for sale securities	3.13%
Weighted-average yield, GAAP basis, held to maturity securities	3.72%
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
1 year or less	628
After 1 year through 5 years	4,255
After 5 years through 10 years	4,516
After 10 years	37,480
Total	46,879	49,080
Available-for-sale Securities, Fair value	635
Available-for-sale Securities, Fair value	4,356
Available-for-sale Securities, Fair value	4,658
Available-for-sale Securities, Fair value	37,953
Available-for-sale Securities, Fair value	47,602	50,685
After 1 year through 5 years	569
After 5 years through 10 years	1,544
After 10 years	7,437
Total	9,550	10,354
Held-to-maturity Securities, Fair Value	583
Held-to-maturity Securities, Fair Value	1,607
Held-to-maturity Securities, Fair Value	7,559
Held-to-maturity Securities, Fair Value	9,749	10,860
One Year or Less [Member]
Schedule of Available-for-sale Securities [Line Items]
Weighted-average yield, GAAP basis, available for sale securities	2.72%
After One Year Through Five Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Weighted-average yield, GAAP basis, available for sale securities	2.45%
Weighted-average yield, GAAP basis, held to maturity securities	3.32%
After Five Years Through Ten Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Weighted-average yield, GAAP basis, available for sale securities	2.38%
Weighted-average yield, GAAP basis, held to maturity securities	3.42%
After Ten Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Weighted-average yield, GAAP basis, available for sale securities	3.30%
Weighted-average yield, GAAP basis, held to maturity securities	3.82%
US Treasury and Government Agencies Securities [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
1 year or less	1
After 1 year through 5 years	1,082
After 5 years through 10 years	804
After 10 years	165
Total	2,052
After 10 years	234
Total	234
Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
After 1 year through 5 years	33
After 5 years through 10 years	513
After 10 years	23,368
Total	23,915
After 10 years	3,773
Total	3,773
Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
After 5 years through 10 years	2
After 10 years	5,802
Total	5,816
Asset backed [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
After 1 year through 5 years	1,088
After 5 years through 10 years	2,138
After 10 years	2,805
Total	6,036
After 1 year through 5 years	60
After 5 years through 10 years	80
After 10 years	960
Total	1,100
State and Municipal [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
1 year or less	12
After 1 year through 5 years	116
After 5 years through 10 years	389
After 10 years	1,676
Total	2,193
After 1 year through 5 years	34
After 5 years through 10 years	282
After 10 years	323
Total	639
Other Debt Securities [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
1 year or less	524
After 1 year through 5 years	1,337
After 5 years through 10 years	529
After 10 years	343
Total	2,733
After 1 year through 5 years	1
After 5 years through 10 years	348
Total	349
Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
1 year or less	1
Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
After 1 year through 5 years	12
Commercial Mortgage Backed Securities [Member] | Mortgage-backed Securities Agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
1 year or less	10
After 1 year through 5 years	528
After 5 years through 10 years	36
Total	574
After 1 year through 5 years	423
After 5 years through 10 years	834
After 10 years	5
Total	1,262
Commercial Mortgage Backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
1 year or less	75
After 1 year through 5 years	59
After 5 years through 10 years	105
After 10 years	3,321
Total	3,560
After 1 year through 5 years	51
After 10 years	2,142
Total	2,193
Asset backed [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
1 year or less	$ 5