Derivatives and Hedging Activities (Details 3) (USD $)			6 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2011 2011	Jun. 30, 2011 2012	Jun. 30, 2011 2013	Jun. 30, 2011 2014	Jun. 30, 2011 2015	Jun. 30, 2011 2016-2025
Summary of Option Premiums Payable and Receivable
Premiums Payable			$ 151,000,000	$ 285,000,000	$ 262,000,000	$ 236,000,000	$ 212,000,000	$ 813,000,000
Premiums Receivable			21,000,000	40,000,000	25,000,000	22,000,000	21,000,000	38,000,000
Gross notional amount of index options and futures contracts	1,400,000,000	1,500,000,000
Gross notional amount of futures and total return swaps	152,000,000	174,000,000
Gross notional amount of foreign currency forward contracts	24,000,000	21,000,000
Gross notional amount of total return swap to hedge equity price risk	$ 35,000,000	$ 35,000,000