Insurance Liabilities - Components of Contractholder Funds (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Liabilities for investment contracts:
Liabilities for individual annuities	$ 10,147.4	$ 10,077.7
GICs	10,222.8	10,115.3
Funding agreements	6,863.4	7,338.1
Other investment contracts	2,007.4	901.6
Total liabilities for investment contracts	29,241.0	28,432.7
Universal life and other reserves	6,475.1	6,294.0
Contractholder funds	$ 35,716.1	$ 34,726.7