Investment Securities (Investments Classified by Contractual Maturity Date) (Details) (USD $) In Millions, unless otherwise specified	Jun. 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	$ 141	$ 166
Available-for-sale debt securities, Due after one year through five years, Amount	2,748	3,001
Available-for-sale debt securities, Due after five years through ten years, Amount	1,809	1,842
Available-for-sale debt securities, Due after ten years, Amount	11,200	11,130
Amortized cost of available-for-sale debt securities, Due in one year or less, Amount	141	165
Amortized cost of available-for-sale debt securities, Due after one year through five years, Amount	2,728	3,000
Available-for-sale Securities, Debt Maturities, after Five Through Ten Years, Amortized Cost Basis	1,802	1,882
Amortized cost of available-for-sale debt securities, Due after ten years, Amount	11,312	11,480
Available-for-sale debt securities, Yield	2.50%	2.50%
Available-for-sale debt securities, Due in one year or less, Yield	2.50%	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	2.50%	2.50%
Available-for-sale debt securities, Due after ten years, Yield	2.70%	2.70%
Available-for-sale Debt Securities, Amortized Cost Basis	15,983	16,527
Available-for-sale Securities, Debt Securities	15,898	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	4	9
Available-for-sale debt securities, Due after one year through five years, Amount	584	766
Available-for-sale debt securities, Due after five years through ten years, Amount	680	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	4.30%	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	1.40%	1.30%
Available-for-sale debt securities, Due after ten years, Yield	0.00%	0.00%
Available-for-sale Debt Securities, Amortized Cost Basis	1,294	1,495
Available-for-sale Securities, Debt Securities	1,268	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	39	39
Available-for-sale debt securities, Due after one year through five years, Amount	10	10
Available-for-sale debt securities, Due after five years through ten years, Amount	124	102
Available-for-sale debt securities, Due after ten years, Amount	213	164
Available-for-sale debt securities, Yield	3.50%	3.30%
Available-for-sale debt securities, Due in one year or less, Yield	2.20%	1.30%
Available-for-sale debt securities, Due after one year through five years, Yield	1.70%	0.60%
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	4.30%	4.30%
Available-for-sale Debt Securities, Amortized Cost Basis	373	316
Available-for-sale Securities, Debt Securities	386	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	135	105
Available-for-sale debt securities, Due after five years through ten years, Amount	113	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	2.80%	2.90%
Available-for-sale debt securities, Due after ten years, Yield	0.00%	2.70%
Available-for-sale Debt Securities, Amortized Cost Basis	242	287
Available-for-sale Securities, Debt Securities	248	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	72	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	10,609	10,689
Available-for-sale debt securities, Yield	2.70%	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	2.70%	2.70%
Available-for-sale Debt Securities, Amortized Cost Basis	10,805	11,131
Available-for-sale Securities, Debt Securities	10,681	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	163	39
Available-for-sale debt securities, Yield	1.40%	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	1.40%	1.30%
Available-for-sale Debt Securities, Amortized Cost Basis	163	39
Available-for-sale Securities, Debt Securities	163	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	62	76
Available-for-sale debt securities, Due after one year through five years, Amount	1,452	1,483
Available-for-sale debt securities, Due after five years through ten years, Amount	469	491
Available-for-sale debt securities, Due after ten years, Amount	157	169
Available-for-sale debt securities, Yield	2.00%	2.00%
Available-for-sale debt securities, Due in one year or less, Yield	2.40%	2.40%
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	2.00%	1.90%
Available-for-sale debt securities, Due after ten years, Yield	2.50%	2.70%
Available-for-sale Debt Securities, Amortized Cost Basis	2,126	2,207
Available-for-sale Securities, Debt Securities	2,140	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	36	24
Available-for-sale debt securities, Due after one year through five years, Amount	495	547
Available-for-sale debt securities, Due after five years through ten years, Amount	423	430
Available-for-sale debt securities, Due after ten years, Amount	58	68
Available-for-sale debt securities, Yield	4.10%	4.10%
Available-for-sale debt securities, Due in one year or less, Yield	2.80%	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	5.20%	5.30%
Available-for-sale debt securities, Due after ten years, Yield	5.90%	5.70%
Available-for-sale Debt Securities, Amortized Cost Basis	980	1,052
Available-for-sale Securities, Debt Securities	$ 1,012	$ 1,069