Derivatives and Hedging Activities (Details 4) (USD $)			6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 2012	Jun. 30, 2012 2013	Jun. 30, 2012 2014	Jun. 30, 2012 2015	Jun. 30, 2012 2016	Jun. 30, 2012 2017-2026
Summary of Option Premiums Payable and Receivable
Premiums Payable			$ 187,000,000	$ 358,000,000	$ 332,000,000	$ 305,000,000	$ 274,000,000	$ 978,000,000
Premiums Receivable			20,000,000	29,000,000	27,000,000	25,000,000	18,000,000	40,000,000
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	21,000,000	26,000,000
Gross notional amount of total return swap to hedge equity price risk	$ 18,000,000	$ 17,000,000