Consolidated Statements of Financial Position (Parenthetical) (USD $) In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fixed maturities, available-for-sale	$ 48,914.9	$ 50,939.3
Fixed maturities, trading	572.9	626.7
Other investments	2,994.0	3,291.1
Other investments measured at fair value under fair value option	140.5	113.9
Separate account assets	123,800.5	81,653.8
Separate account liabilities	123,800.5	81,653.8
Other liabilities	5,387.2	6,146.1
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	2,500.0	2,500.0
Common stock, issued (in shares)	458.0	453.5
Common stock, outstanding (in shares)	293.9	293.8
Treasury stock (in shares)	164.1	159.7
Series A
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, liquidation preference (in dollars per share)	$ 100	$ 100
Preferred stock, authorized (in shares)	3.0	3.0
Preferred stock, issued (in shares)	3.0	3.0
Preferred stock, outstanding (in shares)	3.0	3.0
Series B
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, liquidation preference (in dollars per share)	$ 25	$ 25
Preferred stock, authorized (in shares)	10.0	10.0
Preferred stock, issued (in shares)	10.0	10.0
Preferred stock, outstanding (in shares)	10.0	10.0
Aggregate consolidated variable interest entities
Fixed maturities, available-for-sale	243.3	194.6
Fixed maturities, trading	110.4	110.4
Other investments	72.6	80.3
Separate account assets	31,999.2
Separate account liabilities	31,999.2
Other liabilities	320.6	302.9
Other liabilities measured at fair value under fair value option	$ 102.2	$ 85.0