Consolidated Statements of Financial Position (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Fixed maturities, available-for-sale	$ 55,281.3	$ 49,966.5
Fixed maturities, trading	656.9	686.8
Equity securities, trading	1,331.1	1,202.7
Real estate	1,474.0	1,451.8
Other investments	4,321.5	3,251.7
Other investments measured at fair value under fair value option	82.1	53.4
Separate account assets	134,736.0	136,978.9
Contractholder funds	37,781.0	35,716.1
Long-term debt	3,270.2	3,265.2
Separate account liabilities	134,736.0	136,978.9
Other liabilities	6,226.9	5,678.4
Redeemable noncontrolling interest	$ 337.1	$ 85.7
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)	468,100,000	466,200,000
Common stock, outstanding (in shares)	288,000,000	291,400,000
Treasury stock (in shares)	180,100,000	174,800,000
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	0
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	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)	0	0
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Aggregate consolidated variable interest entities
Fixed maturities, available-for-sale	$ 242.6	$ 257.4
Fixed maturities, trading	82.4	100.4
Equity securities, trading	689.0	640.9
Real estate	411.9	354.5
Other investments	360.5	29.5
Separate account assets	35,839.9	33,300.4
Contractholder funds	346.9	338.9
Long-term debt	46.5	42.8
Separate account liabilities	35,839.9	33,300.4
Other liabilities	317.0	345.9
Other liabilities measured at fair value under fair value option	58.6	$ 68.1
Redeemable noncontrolling interest	$ 266.6