Investment Securities (Investments Classified by Contractual Maturity Date) (Details) (USD $) In Millions, unless otherwise specified	Mar. 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	$ 183	$ 166
Available-for-sale debt securities, Due after one year through five years, Amount	2,742	3,001
Available-for-sale debt securities, Due after five years through ten years, Amount	1,815	1,842
Available-for-sale debt securities, Due after ten years, Amount	10,649	11,130
Amortized cost of available-for-sale debt securities, Due in one year or less, Amount	182	165
Amortized cost of available-for-sale debt securities, Due after one year through five years, Amount	2,729	3,000
Available-for-sale Securities, Debt Maturities, after Five Through Ten Years, Amortized Cost Basis	1,828	1,882
Amortized cost of available-for-sale debt securities, Due after ten years, Amount	10,872	11,480
Available-for-sale debt securities, Yield	2.60%	2.50%
Available-for-sale debt securities, Due in one year or less, Yield	2.50%	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	2.60%	2.50%
Available-for-sale debt securities, Due after ten years, Yield	2.70%	2.70%
Available-for-sale Debt Securities, Amortized Cost Basis	15,611	16,527
Available-for-sale Securities, Debt Securities	15,389	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	9	9
Available-for-sale debt securities, Due after one year through five years, Amount	573	766
Available-for-sale debt securities, Due after five years through ten years, Amount	666	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	3.00%	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	1.40%	1.30%
Available-for-sale debt securities, Due after ten years, Yield	0.00%	0.00%
Available-for-sale Debt Securities, Amortized Cost Basis	1,293	1,495
Available-for-sale Securities, Debt Securities	1,248	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	42	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	103	102
Available-for-sale debt securities, Due after ten years, Amount	183	164
Available-for-sale debt securities, Yield	3.40%	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	1.20%	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	331	316
Available-for-sale Securities, Debt Securities	338	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	29	18
Available-for-sale debt securities, Due after one year through five years, Amount	90	105
Available-for-sale debt securities, Due after five years through ten years, Amount	160	164
Available-for-sale debt securities, Due after ten years, Amount	1	1
Available-for-sale debt securities, Yield	2.80%	2.70%
Available-for-sale debt securities, Due in one year or less, Yield	2.90%	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	3.00%	2.90%
Available-for-sale debt securities, Due after ten years, Yield	2.80%	2.70%
Available-for-sale Debt Securities, Amortized Cost Basis	275	287
Available-for-sale Securities, Debt Securities	280	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	80	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	10,164	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	3.40%	4.20%
Available-for-sale debt securities, Due after ten years, Yield	2.70%	2.70%
Available-for-sale Debt Securities, Amortized Cost Basis	10,475	11,131
Available-for-sale Securities, Debt Securities	10,244	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	62	39
Available-for-sale debt securities, Yield	1.30%	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	1.30%	1.30%
Available-for-sale Debt Securities, Amortized Cost Basis	61	39
Available-for-sale Securities, Debt Securities	62	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	76	76
Available-for-sale debt securities, Due after one year through five years, Amount	1,456	1,483
Available-for-sale debt securities, Due after five years through ten years, Amount	432	491
Available-for-sale debt securities, Due after ten years, Amount	170	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	2.60%	2.70%
Available-for-sale Debt Securities, Amortized Cost Basis	2,121	2,207
Available-for-sale Securities, Debt Securities	2,134	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	27	24
Available-for-sale debt securities, Due after one year through five years, Amount	533	547
Available-for-sale debt securities, Due after five years through ten years, Amount	454	430
Available-for-sale debt securities, Due after ten years, Amount	69	68
Available-for-sale debt securities, Yield	4.20%	4.10%
Available-for-sale debt securities, Due in one year or less, Yield	3.20%	3.40%
Available-for-sale debt securities, Due after one year through five years, Yield	3.10%	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	5.80%	5.70%
Available-for-sale Debt Securities, Amortized Cost Basis	1,055	1,052
Available-for-sale Securities, Debt Securities	$ 1,083	$ 1,069