Investment Securities (Investments Classified by Contractual Maturity Date) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 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	$ 108	$ 166
Available-for-sale debt securities, Due after one year through five years, Amount	2,676	3,001
Available-for-sale debt securities, Due after five years through ten years, Amount	1,383	1,842
Available-for-sale debt securities, Due after ten years, Amount	11,064	11,130
Amortized cost of available-for-sale debt securities, Due in one year or less, Amount	108	165
Amortized cost of available-for-sale debt securities, Due after one year through five years, Amount	2,674	3,000
Available-for-sale Securities, Debt Maturities, after Five Through Ten Years, Amortized Cost Basis	1,374	1,882
Amortized cost of available-for-sale debt securities, Due after ten years, Amount	11,060	11,480
Available-for-sale debt securities, Yield	2.50%	2.50%
Available-for-sale debt securities, Due in one year or less, Yield	2.70%	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	2.40%	2.50%
Available-for-sale debt securities, Due after ten years, Yield	2.60%	2.70%
Available-for-sale Securities, Debt Securities	15,231	16,139
Available-for-sale Debt Securities, Amortized Cost Basis	15,216	16,527
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	677	766
Available-for-sale debt securities, Due after five years through ten years, Amount	494	652
Available-for-sale debt securities, Due after ten years, Amount	0	0
Available-for-sale debt securities, Yield	1.50%	1.30%
Available-for-sale debt securities, Due in one year or less, Yield	3.00%	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	1.90%	1.30%
Available-for-sale debt securities, Due after ten years, Yield	0.00%	0.00%
Available-for-sale Securities, Debt Securities	1,178	1,427
Available-for-sale Debt Securities, Amortized Cost Basis	1,195	1,495
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	34	39
Available-for-sale debt securities, Due after one year through five years, Amount	12	10
Available-for-sale debt securities, Due after five years through ten years, Amount	106	102
Available-for-sale debt securities, Due after ten years, Amount	254	164
Available-for-sale debt securities, Yield	3.70%	3.30%
Available-for-sale debt securities, Due in one year or less, Yield	1.90%	1.30%
Available-for-sale debt securities, Due after one year through five years, Yield	2.10%	0.60%
Available-for-sale debt securities, Due after five years through ten years, Yield	3.00%	2.60%
Available-for-sale debt securities, Due after ten years, Yield	4.30%	4.30%
Available-for-sale Securities, Debt Securities	406	315
Available-for-sale Debt Securities, Amortized Cost Basis	389	316
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	128	105
Available-for-sale debt securities, Due after five years through ten years, Amount	104	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	2.50%	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 Securities, Debt Securities	232	288
Available-for-sale Debt Securities, Amortized Cost Basis	224	287
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	34	0
Available-for-sale debt securities, Due after one year through five years, Amount	58	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	10,333	10,689
Available-for-sale debt securities, Yield	2.60%	2.70%
Available-for-sale debt securities, Due in one year or less, Yield	3.10%	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	2.60%	2.70%
Available-for-sale Securities, Debt Securities	10,425	10,782
Available-for-sale Debt Securities, Amortized Cost Basis	10,431	11,131
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	30	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	223	39
Available-for-sale debt securities, Yield	1.50%	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	1.80%	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 Securities, Debt Securities	253	39
Available-for-sale Debt Securities, Amortized Cost Basis	254	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	0	76
Available-for-sale debt securities, Due after one year through five years, Amount	1,311	1,483
Available-for-sale debt securities, Due after five years through ten years, Amount	463	491
Available-for-sale debt securities, Due after ten years, Amount	217	169
Available-for-sale debt securities, Yield	1.90%	2.00%
Available-for-sale debt securities, Due in one year or less, Yield	0.00%	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	2.20%	2.70%
Available-for-sale Securities, Debt Securities	1,991	2,219
Available-for-sale Debt Securities, Amortized Cost Basis	1,989	2,207
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Due in one year or less, Amount	33	24
Available-for-sale debt securities, Due after one year through five years, Amount	460	547
Available-for-sale debt securities, Due after five years through ten years, Amount	216	430
Available-for-sale debt securities, Due after ten years, Amount	37	68
Available-for-sale debt securities, Yield	3.20%	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	2.70%	3.00%
Available-for-sale debt securities, Due after five years through ten years, Yield	3.80%	5.30%
Available-for-sale debt securities, Due after ten years, Yield	5.60%	5.70%
Available-for-sale Securities, Debt Securities	746	1,069
Available-for-sale Debt Securities, Amortized Cost Basis	$ 734	$ 1,052