Borrowings (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2011	Dec. 31, 2010
Schedule of Borrowings [Line Items]
Junior subordinated debentures	$ 1,200	$ 1,200
Borrowings (Textual) [Abstract]
Rate on related enhanced trust preferred securities	8.50%
Junior Subordinated Debentures Maturity Date	Jan. 31, 2068
Debt Maturity, Start Date	2027
Debt Maturity, End Date	2068
Period of days prior to redemption or repurchase of enhanced trust preferred securities applicable to provisions of the replacement capital covenant	180 days
End date of restrictions included in the replacement capital covenant	Jan. 31, 2048
Junior Subordinated Debenture due January 31, 2068 [Member]
Schedule of Borrowings [Line Items]
Junior subordinated debentures	$ 350