Consolidated Statements of Financial Position (Parenthetical) (USD $) In Millions, except Per Share data	Jun. 30, 2011	Dec. 31, 2010
Fixed maturities, available-for-sale	$ 48,947.5	$ 48,636.3
Fixed maturities, trading	954.7	1,120.3
Equity securities, trading	429.0	316.9
Other investments	2,767.3	2,641.6
Cash and cash equivalents	2,169.6	1,877.4
Other liabilities	5,737.4	6,143.5
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)	449.7	448.5
Common stock, outstanding (in shares)	313.7	320.4
Treasury stock (in shares)	136.0	128.1
Aggregate consolidated variable interest entities
Fixed maturities, available-for-sale	264.4	257.9
Fixed maturities, trading	135.0	131.4
Equity securities, trading	249.5	158.6
Other investments	107.9	128.7
Other investments measured at fair value under fair value option	107.4	128.3
Cash and cash equivalents	196.2	100.0
Other liabilities	543.5	433.6
Other liabilities measured at fair value under fair value option	$ 98.4	$ 114.5
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