Consolidated Statements of Financial Position (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Fixed maturities, available-for-sale	$ 49,755.7	$ 49,670.8
Fixed maturities, trading	574.0	604.6
Equity securities, trading	875.1	840.2
Real estate	1,391.7	1,344.6
Other investments	3,395.6	3,209.8
Other investments measured at fair value under fair value option	57.5	127.2
Separate account assets	143,505.2	140,072.8
Long-term debt	2,514.6	2,531.2
Separate account liabilities	143,505.2	140,072.8
Other liabilities	5,506.3	5,542.2
Other liabilities measured at fair value under fair value option	67.1	71.0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	2,500,000,000	2,500,000,000
Common stock, issued (in shares)	464,700,000	462,700,000
Common stock, outstanding (in shares)	294,400,000	293,900,000
Treasury stock (in shares)	170,300,000	168,800,000
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)	3,000,000	3,000,000
Preferred stock, issued (in shares)	3,000,000	3,000,000
Preferred stock, outstanding (in shares)	3,000,000	3,000,000
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)	10,000,000	10,000,000
Preferred stock, issued (in shares)	10,000,000	10,000,000
Preferred stock, outstanding (in shares)	10,000,000	10,000,000
Aggregate consolidated variable interest entities
Fixed maturities, available-for-sale	266.4	278.2
Fixed maturities, trading	100.4	100.4
Equity securities, trading	352.3	345.3
Real estate	297.8	284.9
Other investments	34.6	40.6
Separate account assets	35,319.4	34,655.4
Long-term debt	65.6	82.3
Separate account liabilities	35,319.4	34,655.4
Other liabilities	$ 335.9	$ 344.0