Derivatives and Hedging Activities (Details 3) (USD $)			12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 2012	Dec. 31, 2011 2013	Dec. 31, 2011 2014	Dec. 31, 2011 2015	Dec. 31, 2011 2016	Dec. 31, 2011 2017-2026
Summary of Option Premiums Payable and Receivable
Premiums Payable			$ 372,000,000	$ 349,000,000	$ 324,000,000	$ 296,000,000	$ 265,000,000	$ 925,000,000
Premiums Receivable			41,000,000	26,000,000	24,000,000	22,000,000	15,000,000	34,000,000
Gross notional amount of index options and futures contracts	1,300,000,000	1,500,000,000
Gross notional amount of futures and total return swaps	123,000,000	174,000,000
Gross notional amount of foreign currency forward contracts	26,000,000	21,000,000
Gross notional amount of total return swap to hedge equity price risk	$ 17,000,000	$ 35,000,000