Investment Securities (Investments Classified by Contractual Maturity Date) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Due in one year or less, Amount	$ 103	$ 166
Available-for-sale debt securities, Due after one year through five years, Amount	2,775	3,001
Available-for-sale debt securities, Due after five years through ten years, Amount	1,596	1,842
Available-for-sale debt securities, Due after ten years, Amount	11,512	11,130
Amortized cost of available-for-sale debt securities, Due in one year or less, Amount	102	165
Amortized cost of available-for-sale debt securities, Due after one year through five years, Amount	2,773	3,000
Available-for-sale Securities, Debt Maturities, after Five Through Ten Years, Amortized Cost Basis	1,596	1,882
Amortized cost of available-for-sale debt securities, Due after ten years, Amount	11,637	11,480
Available-for-sale debt securities, Yield	2.60%	2.50%
Available-for-sale debt securities, Due in one year or less, Yield	2.20%	2.30%
Available-for-sale debt securities, Due after one year through five years, Yield	1.90%	1.90%
Available-for-sale debt securities, Due after five years through ten years, Yield	2.60%	2.50%
Available-for-sale debt securities, Due after ten years, Yield	2.80%	2.70%
Available-for-sale Debt Securities, Amortized Cost Basis	16,108	16,527
Available-for-sale Securities, Debt Securities	15,986	16,139
US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Due in one year or less, Amount	7	9
Available-for-sale debt securities, Due after one year through five years, Amount	791	766
Available-for-sale debt securities, Due after five years through ten years, Amount	488	652
Available-for-sale debt securities, Due after ten years, Amount	0	0
Available-for-sale debt securities, Yield	1.30%	1.30%
Available-for-sale debt securities, Due in one year or less, Yield	3.10%	3.00%
Available-for-sale debt securities, Due after one year through five years, Yield	1.20%	1.20%
Available-for-sale debt securities, Due after five years through ten years, Yield	1.50%	1.30%
Available-for-sale debt securities, Due after ten years, Yield	0.00%	0.00%
Available-for-sale Debt Securities, Amortized Cost Basis	1,313	1,495
Available-for-sale Securities, Debt Securities	1,286	1,427
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Due in one year or less, Amount	36	39
Available-for-sale debt securities, Due after one year through five years, Amount	15	10
Available-for-sale debt securities, Due after five years through ten years, Amount	108	102
Available-for-sale debt securities, Due after ten years, Amount	243	164
Available-for-sale debt securities, Yield	3.50%	3.30%
Available-for-sale debt securities, Due in one year or less, Yield	1.20%	1.30%
Available-for-sale debt securities, Due after one year through five years, Yield	2.00%	0.60%
Available-for-sale debt securities, Due after five years through ten years, Yield	2.80%	2.60%
Available-for-sale debt securities, Due after ten years, Yield	4.30%	4.30%
Available-for-sale Debt Securities, Amortized Cost Basis	386	316
Available-for-sale Securities, Debt Securities	402	315
Foreign Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Due in one year or less, Amount	0	18
Available-for-sale debt securities, Due after one year through five years, Amount	124	105
Available-for-sale debt securities, Due after five years through ten years, Amount	108	164
Available-for-sale debt securities, Due after ten years, Amount	0	1
Available-for-sale debt securities, Yield	2.70%	2.70%
Available-for-sale debt securities, Due in one year or less, Yield	0.00%	2.70%
Available-for-sale debt securities, Due after one year through five years, Yield	2.60%	2.40%
Available-for-sale debt securities, Due after five years through ten years, Yield	2.90%	2.90%
Available-for-sale debt securities, Due after ten years, Yield	0.00%	2.70%
Available-for-sale Debt Securities, Amortized Cost Basis	226	287
Available-for-sale Securities, Debt Securities	232	288
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
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	65	90
Available-for-sale debt securities, Due after five years through ten years, Amount	0	3
Available-for-sale debt securities, Due after ten years, Amount	10,819	10,689
Available-for-sale debt securities, Yield	2.80%	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	2.10%	2.10%
Available-for-sale debt securities, Due after five years through ten years, Yield	0.00%	4.20%
Available-for-sale debt securities, Due after ten years, Yield	2.80%	2.70%
Available-for-sale Debt Securities, Amortized Cost Basis	11,018	11,131
Available-for-sale Securities, Debt Securities	10,884	10,782
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
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	0	0
Available-for-sale debt securities, Due after ten years, Amount	212	39
Available-for-sale debt securities, Yield	2.10%	1.30%
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	0.00%	0.00%
Available-for-sale debt securities, Due after ten years, Yield	2.10%	1.30%
Available-for-sale Debt Securities, Amortized Cost Basis	213	39
Available-for-sale Securities, Debt Securities	212	39
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Due in one year or less, Amount	26	76
Available-for-sale debt securities, Due after one year through five years, Amount	1,300	1,483
Available-for-sale debt securities, Due after five years through ten years, Amount	479	491
Available-for-sale debt securities, Due after ten years, Amount	182	169
Available-for-sale debt securities, Yield	2.00%	2.00%
Available-for-sale debt securities, Due in one year or less, Yield	2.30%	2.40%
Available-for-sale debt securities, Due after one year through five years, Yield	2.00%	1.90%
Available-for-sale debt securities, Due after five years through ten years, Yield	1.90%	1.90%
Available-for-sale debt securities, Due after ten years, Yield	2.50%	2.70%
Available-for-sale Debt Securities, Amortized Cost Basis	1,982	2,207
Available-for-sale Securities, Debt Securities	1,987	2,219
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Due in one year or less, Amount	34	24
Available-for-sale debt securities, Due after one year through five years, Amount	480	547
Available-for-sale debt securities, Due after five years through ten years, Amount	413	430
Available-for-sale debt securities, Due after ten years, Amount	56	68
Available-for-sale debt securities, Yield	3.90%	4.10%
Available-for-sale debt securities, Due in one year or less, Yield	3.10%	3.40%
Available-for-sale debt securities, Due after one year through five years, Yield	3.00%	3.00%
Available-for-sale debt securities, Due after five years through ten years, Yield	4.90%	5.30%
Available-for-sale debt securities, Due after ten years, Yield	5.80%	5.70%
Available-for-sale Debt Securities, Amortized Cost Basis	970	1,052
Available-for-sale Securities, Debt Securities	$ 983	$ 1,069