Derivatives and Hedging Activities (Details 4) (USD $)			3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 April 1, 2013 to December 31, 2013	Mar. 31, 2013 2014	Mar. 31, 2013 2015	Mar. 31, 2013 2016	Mar. 31, 2013 2017	Mar. 31, 2013 2018-2027
Summary of Option Premiums Payable and Receivable
Premiums Payable			$ 287,000,000	$ 344,000,000	$ 317,000,000	$ 287,000,000	$ 237,000,000	$ 780,000,000
Premiums Receivable			47,000,000	54,000,000	53,000,000	46,000,000	40,000,000	104,000,000
Gross notional amount of index options and futures contracts	1,400,000,000	1,300,000,000
Gross notional amount of forwards, futures, total return swaps and commodity swaps	194,000,000	146,000,000
Gross notional amount of foreign currency forward contracts	$ 17,000,000	$ 14,000,000