Investments (Details 3) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Fixed maturities, available-for-sale:
Gross gains	$ 3,000,000	$ 5,400,000	$ 22,700,000	$ 23,600,000
Gross losses	(44,100,000)	(13,300,000)	(131,000,000)	(74,500,000)
Other-than-temporary impairment losses on fixed maturities, available-for-sale reclassified to (from) other comprehensive income	9,200,000	(34,900,000)	31,200,000	(83,000,000)
Hedging, net	1,000,000	110,100,000	7,700,000	139,600,000
Fixed maturities, trading	4,700,000	(11,200,000)	5,700,000	(12,500,000)
Equity securities, available-for-sale:
Gross gains	500,000	100,000	600,000	2,300,000
Gross losses	(600,000)		(600,000)	(4,500,000)
Equity securities, trading	(100,000)	(35,800,000)	30,600,000	20,800,000
Mortgage loans	(23,300,000)	(13,000,000)	(44,600,000)	(35,000,000)
Derivatives	(50,500,000)	(105,700,000)	(20,100,000)	(161,400,000)
Other	187,900,000	67,600,000	179,000,000	133,600,000
Net realized capital gains (losses)	87,700,000	(30,700,000)	81,200,000	(51,000,000)
Proceeds from sales of investments
Proceeds from sales of investments in fixed maturities, available-for-sale	$ 300,000,000	$ 100,000,000	$ 1,000,000,000	$ 800,000,000