Commercial Paper Commercial Paper (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Line of Credit Facility [Line Items]
Interest expense for commercial paper	$ 5,000,000	$ 9,000,000	$ 11,000,000
Tangible common equity to tangible assets ratio	6.75%
Debt extended to us from affiliates	5,000,000,000
Commercial Paper [Member]
Line of Credit Facility [Line Items]
Commercial paper back-up lines of credit	2,100,000,000	6,000,000,000
Annual commitment fees expense	27,000,000	19,000,000	33,000,000
Commercial Paper [Member] | HSBC USA Inc [Member]
Line of Credit Facility [Line Items]
Commercial paper back-up lines of credit	100,000,000	2,000,000,000
Annual commitment fees expense	$ 20,000,000	$ 10,000,000	$ 16,000,000