Derivatives and Hedging Activities (Details 4) (USD $)			3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2012 2012	Mar. 31, 2012 2013	Mar. 31, 2012 2014	Mar. 31, 2012 2015	Mar. 31, 2012 2016	Mar. 31, 2012 2017-2026
Summary of Option Premiums Payable and Receivable
Premiums Payable			$ 295,000,000	$ 357,000,000	$ 332,000,000	$ 304,000,000	$ 273,000,000	$ 972,000,000
Premiums Receivable			32,000,000	26,000,000	24,000,000	22,000,000	15,000,000	35,000,000
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	117,000,000	123,000,000
Gross notional amount of foreign currency forward contracts	26,000,000	26,000,000
Gross notional amount of total return swap to hedge equity price risk	$ 20,000,000	$ 17,000,000