Separate Accounts, Death Benefits and Other Insurance Benefit Features and Embedded Product Derivatives - Changes in Liability Balances (Details) - Universal Life - USD ($) $ in Millions	3 Months Ended		6 Months Ended	12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Dec. 31, 2014
Supplementary Insurance Information, Liability for Future Policy Benefits, Losses, Claims and Loss Expense Reserves [Roll Forward]
Balance, beginning of period	$ 397.6	$ 300.3	$ 366.6	$ 270.3
Incurred	(1.8)	18.1	10.3	34.5
Assumption unlocking	0.0	0.0	(4.6)	0.0
Change due to net unrealized gains or losses included in AOCI	(25.2)	(8.3)	(1.7)	5.3
Balance, end of period	$ 370.6	$ 310.1	$ 370.6	$ 366.6