Derivatives and Hedging Activities (Details 4) (USD $)			9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 2012	Sep. 30, 2012 2013	Sep. 30, 2012 2014	Sep. 30, 2012 2015	Sep. 30, 2012 2016	Sep. 30, 2012 2017-2026
Summary of Option Premiums Payable and Receivable
Premiums Payable			$ 110,000,000	$ 371,000,000	$ 345,000,000	$ 318,000,000	$ 287,000,000	$ 1,022,000,000
Premiums Receivable			9,000,000	36,000,000	34,000,000	32,000,000	25,000,000	84,000,000
Gross notional amount of index options and futures contracts	1,300,000,000	1,300,000,000
Gross notional amount of futures and total return swaps	114,000,000	123,000,000
Gross notional amount of foreign currency forward contracts	18,000,000	26,000,000
Gross notional amount of total return swap to hedge equity price risk	19,000,000	17,000,000
Notional amount of interest rate swaps	$ 1,600,000,000