Investment Securities (Investments Classified by Contractual Maturity Date) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	$ 17,015	$ 14,178
Available-for-sale Securities, Amortized Cost Basis	17,294	13,997
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	15,995	13,026
Available-for-sale debt securities, Due in one year or less, Amount	384	432
Available-for-sale debt securities, Due after one year through five years, Amount	2,911	2,921
Available-for-sale debt securities, Due after five years through ten years, Amount	2,310	2,417
Available-for-sale debt securities, Due after ten years, Amount	10,390	7,256
Available-for-sale Securities, Amortized Cost Basis	16,243	12,804
Amortized cost of available-for-sale debt securities, Due in one year or less, Amount	384	431
Amortized cost of available-for-sale debt securities, Due after one year through five years, Amount	2,898	2,880
Available-for-sale Securities, Debt Maturities, after Five Through Ten Years, Amortized Cost Basis	2,342	2,369
Amortized cost of available-for-sale debt securities, Due after ten years, Amount	10,619	7,124
Available-for-sale debt securities, Yield	2.50%	2.40%
Available-for-sale debt securities, Due in one year or less, Yield	0.70%	0.10%
Available-for-sale debt securities, Due after one year through five years, Yield	2.20%	2.00%
Available-for-sale debt securities, Due after five years through ten years, Yield	2.70%	2.60%
Available-for-sale debt securities, Due after ten years, Yield	2.60%	2.60%
US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	1,790	2,214
Available-for-sale debt securities, Due in one year or less, Amount	349	422
Available-for-sale debt securities, Due after one year through five years, Amount	507	682
Available-for-sale debt securities, Due after five years through ten years, Amount	934	1,110
Available-for-sale debt securities, Due after ten years, Amount	0	0
Available-for-sale Securities, Amortized Cost Basis	1,840	2,212
Available-for-sale debt securities, Yield	1.10%	0.90%
Available-for-sale debt securities, Due in one year or less, Yield	0.10%	0.00%
Available-for-sale debt securities, Due after one year through five years, Yield	1.20%	0.70%
Available-for-sale debt securities, Due after five years through ten years, Yield	1.30%	1.40%
Available-for-sale debt securities, Due after ten years, Yield	0.00%	0.00%
Foreign Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	292	303
Available-for-sale debt securities, Due in one year or less, Amount	10	1
Available-for-sale debt securities, Due after one year through five years, Amount	111	136
Available-for-sale debt securities, Due after five years through ten years, Amount	171	166
Available-for-sale debt securities, Due after ten years, Amount	0	0
Available-for-sale Securities, Amortized Cost Basis	290	295
Available-for-sale debt securities, Yield	3.90%	2.50%
Available-for-sale debt securities, Due in one year or less, Yield	7.40%	2.20%
Available-for-sale debt securities, Due after one year through five years, Yield	4.30%	1.80%
Available-for-sale debt securities, Due after five years through ten years, Yield	3.50%	3.00%
Available-for-sale debt securities, Due after ten years, Yield	0.00%	0.00%
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	10,328	6,906
Available-for-sale debt securities, Due in one year or less, Amount	0	0
Available-for-sale debt securities, Due after one year through five years, Amount	0	0
Available-for-sale debt securities, Due after five years through ten years, Amount	113	35
Available-for-sale debt securities, Due after ten years, Amount	10,215	6,871
Available-for-sale Securities, Amortized Cost Basis	10,558	6,779
Available-for-sale debt securities, Yield	2.60%	2.70%
Available-for-sale debt securities, Due in one year or less, Yield	0.00%	0.00%
Available-for-sale debt securities, Due after one year through five years, Yield	0.00%	0.00%
Available-for-sale debt securities, Due after five years through ten years, Yield	2.10%	4.30%
Available-for-sale debt securities, Due after ten years, Yield	2.60%	2.70%
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	2,276	2,340
Available-for-sale debt securities, Due in one year or less, Amount	0	0
Available-for-sale debt securities, Due after one year through five years, Amount	1,700	1,543
Available-for-sale debt securities, Due after five years through ten years, Amount	484	510
Available-for-sale debt securities, Due after ten years, Amount	92	287
Available-for-sale Securities, Amortized Cost Basis	2,258	2,309
Available-for-sale debt securities, Yield	1.90%	2.10%
Available-for-sale debt securities, Due in one year or less, Yield	0.00%	0.00%
Available-for-sale debt securities, Due after one year through five years, Yield	1.90%	2.00%
Available-for-sale debt securities, Due after five years through ten years, Yield	1.80%	1.70%
Available-for-sale debt securities, Due after ten years, Yield	2.60%	3.30%
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	1,309	1,263
Available-for-sale debt securities, Due in one year or less, Amount	25	9
Available-for-sale debt securities, Due after one year through five years, Amount	593	560
Available-for-sale debt securities, Due after five years through ten years, Amount	608	596
Available-for-sale debt securities, Due after ten years, Amount	83	98
Available-for-sale Securities, Amortized Cost Basis	$ 1,297	$ 1,209
Available-for-sale debt securities, Yield	5.00%	5.10%
Available-for-sale debt securities, Due in one year or less, Yield	6.60%	3.20%
Available-for-sale debt securities, Due after one year through five years, Yield	4.00%	4.00%
Available-for-sale debt securities, Due after five years through ten years, Yield	5.60%	6.00%
Available-for-sale debt securities, Due after ten years, Yield	5.90%	5.80%