Investment Securities (Investments, by type and length in continuous loss position) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Percent of Gross unrealized losses, 12 months or more, considered investment grade	70.00%
OTTI previously recognized through OCI on securities held, gross unrealized losses	$ (85)
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Residential Mortgage Backed Securities [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Debt securities, Estimated fair value	649
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Residential Mortgage Backed Securities [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Debt securities, Estimated fair value	1,225
Domestic Corporate Debt Securities [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months	1,578	2,170
Gross unrealized losses, less than 12 months	(63)	(122)
Estimated fair value, 12 months or more	563	598
Gross unrealized losses, 12 months or more	(75)	(95)
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months	942	1,076
Gross unrealized losses, less than 12 months	(37)	(82)
Estimated fair value, 12 months or more	347	367
Gross unrealized losses, 12 months or more	(93)	(109)
Residential Mortgage Backed Securities [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months	187	232
Gross unrealized losses, less than 12 months	(6)	(11)
Estimated fair value, 12 months or more	430	430
Gross unrealized losses, 12 months or more	(33)	(37)
Mortgage-backed Securities, Residential, Subprime, Financing Receivable [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Debt securities, Estimated fair value	355
Commercial Mortgage Backed Securities [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months	254	396
Gross unrealized losses, less than 12 months	(11)	(24)
Estimated fair value, 12 months or more	803	780
Gross unrealized losses, 12 months or more	(50)	(58)
Asset-backed Securities [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months	101	112
Gross unrealized losses, less than 12 months	(1)	(2)
Estimated fair value, 12 months or more	294	359
Gross unrealized losses, 12 months or more	(40)	(44)
Foreign Corporate Debt Securities [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months	56	108
Gross unrealized losses, less than 12 months	(1)	(4)
Estimated fair value, 12 months or more	430	454
Gross unrealized losses, 12 months or more	(63)	(83)
Foreign Government Debt Securities [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months	1,098	1,479
Gross unrealized losses, less than 12 months	(3)	(6)
Estimated fair value, 12 months or more	52	42
Gross unrealized losses, 12 months or more	0	(1)
US Treasury and Government [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months	238	229
Gross unrealized losses, less than 12 months	(18)	(27)
Estimated fair value, 12 months or more	0	254
Gross unrealized losses, 12 months or more	0	0
Retained Interest [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months	1	2
Gross unrealized losses, less than 12 months	0	0
Estimated fair value, 12 months or more	1	0
Gross unrealized losses, 12 months or more	0	0
Equity Securities [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months	250	253
Gross unrealized losses, less than 12 months	(78)	(44)
Estimated fair value, 12 months or more	0	0
Gross unrealized losses, 12 months or more	0	0
Total [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months	4,705	6,057
Gross unrealized losses, less than 12 months	(218)	(322)
Estimated fair value, 12 months or more	2,920	3,284
Gross unrealized losses, 12 months or more	(354)	(427)
Subsidiaries [Member] | Foreign Corporate Debt Securities [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months	13	12
Gross unrealized losses, less than 12 months		1
Insignificant gross unrealized losses, less than 12 months	an insignificant amount
Subsidiaries [Member] | Equity Securities [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months	210	222
Gross unrealized losses, less than 12 months	$ 70	$ 41