Investment Securities (Investments, by type and length in continuous loss position) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months	$ 9,319	$ 6,057
Gross unrealized losses, less than 12 months	(241)	(322)
Estimated fair value, 12 months or more	3,971	3,284
Gross unrealized losses, 12 months or more	(318)	(427)
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	(55)
Domestic Corporate Debt Securities [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months	647	2,170
Gross unrealized losses, less than 12 months	(8)	(122)
Estimated fair value, 12 months or more	1,433	598
Gross unrealized losses, 12 months or more	(91)	(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	134	1,076
Gross unrealized losses, less than 12 months	(2)	(82)
Estimated fair value, 12 months or more	649	367
Gross unrealized losses, 12 months or more	(87)	(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	96	232
Gross unrealized losses, less than 12 months	(1)	(11)
Estimated fair value, 12 months or more	436	430
Gross unrealized losses, 12 months or more	(24)	(37)
Residential Mortgage Backed Securities [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Debt securities, Estimated fair value	610
Residential Mortgage Backed Securities [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Debt securities, Estimated fair value	1,218
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	316
Commercial Mortgage Backed Securities [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months	126	396
Gross unrealized losses, less than 12 months	(1)	(24)
Estimated fair value, 12 months or more	853	780
Gross unrealized losses, 12 months or more	(39)	(58)
Asset-backed Securities [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months	7,172	112
Gross unrealized losses, less than 12 months	(86)	(2)
Estimated fair value, 12 months or more	274	359
Gross unrealized losses, 12 months or more	(33)	(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	29	108
Gross unrealized losses, less than 12 months	0	(4)
Estimated fair value, 12 months or more	317	454
Gross unrealized losses, 12 months or more	(44)	(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	880	1,479
Gross unrealized losses, less than 12 months	(2)	(6)
Estimated fair value, 12 months or more	2	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	0	229
Gross unrealized losses, less than 12 months	0	(27)
Estimated fair value, 12 months or more	7	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	0	2
Gross unrealized losses, less than 12 months	0	0
Estimated fair value, 12 months or more	0	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	235	253
Gross unrealized losses, less than 12 months	(141)	(44)
Estimated fair value, 12 months or more	0	0
Gross unrealized losses, 12 months or more	0	0
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		12
Gross unrealized losses, less than 12 months		(1)
Subsidiaries [Member] | Equity Securities [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months	149	222
Gross unrealized losses, less than 12 months	$ (131)	$ (41)