Consolidated Statements of Financial Position (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Fixed maturities, available-for-sale	$ 49,780.6	$ 49,670.8
Fixed maturities, trading	710.2	604.6
Equity securities, available-for-sale	465.3	123.0
Equity securities, trading	869.1	840.2
Real estate	1,415.0	1,344.6
Other investments	3,270.4	3,209.8
Other investments measured at fair value under fair value option	56.6	127.2
Separate account assets	134,045.8	140,072.8
Contractholder funds	35,115.2	34,726.7
Long-term debt	3,286.1	2,531.2
Separate account liabilities	134,045.8	140,072.8
Other liabilities	$ 5,696.2	$ 5,542.2
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)	466,000,000	462,700,000
Common stock, outstanding (in shares)	293,500,000	293,900,000
Treasury stock (in shares)	172,500,000	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)	0	3,000,000
Preferred stock, issued (in shares)	0	3,000,000
Preferred stock, outstanding (in shares)	0	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)	0	10,000,000
Preferred stock, issued (in shares)	0	10,000,000
Preferred stock, outstanding (in shares)	0	10,000,000
Aggregate consolidated variable interest entities
Fixed maturities, available-for-sale	$ 261.1	$ 278.2
Fixed maturities, trading	100.4	100.4
Equity securities, available-for-sale	315.8
Equity securities, trading	321.2	345.3
Real estate	298.9	284.9
Other investments	36.8	40.6
Separate account assets	32,827.6	34,655.4
Contractholder funds	329.2
Long-term debt	38.2	82.3
Separate account liabilities	32,827.6	34,655.4
Other liabilities	340.7	344.0
Other liabilities measured at fair value under fair value option	$ 64.7	$ 71.0