Consolidated Statements of Financial Position (Parenthetical) (USD $) In Millions, except Per Share data, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fixed maturities, available-for-sale	$ 49,191.6	$ 50,939.3
Fixed maturities, trading	589.8	626.7
Other investments	2,976.3	3,291.1
Other investments measured at fair value under fair value option	116.5	113.9
Separate account assets	118,740.2	81,653.8
Separate account liabilities	118,740.2	81,653.8
Other liabilities	5,831.5	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)	456.5	453.5
Common stock, outstanding (in shares)	293.9	293.8
Treasury stock (in shares)	162.6	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	232.8	194.6
Fixed maturities, trading	110.4	110.4
Other investments	76.6	80.3
Separate account assets	33,179.6
Separate account liabilities	33,179.6
Other liabilities	314.4	302.9
Other liabilities measured at fair value under fair value option	$ 98.9	$ 85.0