Investment Securities (Schedule of Available-for-sale Securities Reconciliation) (Details) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 17,294,000,000	$ 13,997,000,000
Available-for-sale Securities, Gross Unrealized Gains	130,000,000	262,000,000
Available-for-sale Securities, Gross Unrealized Losses	(409,000,000)	(81,000,000)
Available-for-sale Securities	17,015,000,000	14,178,000,000
Total agency backed bonds	7,720,000,000	4,983,000,000
Deposit Assets	15,000,000	15,000,000
Cash Equivalents, at Carrying Value	3,200,000,000	3,400,000,000
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	16,243,000,000	12,804,000,000
Available-for-sale Securities, Gross Unrealized Gains	90,000,000	230,000,000
Available-for-sale Securities, Gross Unrealized Losses	(338,000,000)	(8,000,000)
Available-for-sale Securities	15,995,000,000	13,026,000,000
US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,840,000,000	2,212,000,000
Available-for-sale Securities, Gross Unrealized Gains	1,000,000	3,000,000
Available-for-sale Securities, Gross Unrealized Losses	(51,000,000)	(1,000,000)
Available-for-sale Securities	1,790,000,000	2,214,000,000
Foreign Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	290,000,000	295,000,000
Available-for-sale Securities, Gross Unrealized Gains	4,000,000	8,000,000
Available-for-sale Securities, Gross Unrealized Losses	(2,000,000)	0
Available-for-sale Securities	292,000,000	303,000,000
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	10,558,000,000	6,779,000,000
Available-for-sale Securities, Gross Unrealized Gains	39,000,000	130,000,000
Available-for-sale Securities, Gross Unrealized Losses	(269,000,000)	(3,000,000)
Available-for-sale Securities	10,328,000,000	6,906,000,000
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	2,258,000,000	2,309,000,000
Available-for-sale Securities, Gross Unrealized Gains	22,000,000	32,000,000
Available-for-sale Securities, Gross Unrealized Losses	(4,000,000)	(1,000,000)
Available-for-sale Securities	2,276,000,000	2,340,000,000
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,297,000,000	1,209,000,000
Available-for-sale Securities, Gross Unrealized Gains	24,000,000	57,000,000
Available-for-sale Securities, Gross Unrealized Losses	(12,000,000)	(3,000,000)
Available-for-sale Securities	1,309,000,000	1,263,000,000
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,051,000,000	1,193,000,000
Available-for-sale Securities, Gross Unrealized Gains	40,000,000	32,000,000
Available-for-sale Securities, Gross Unrealized Losses	(71,000,000)	(73,000,000)
Available-for-sale Securities	$ 1,020,000,000	$ 1,152,000,000