Deferred Policy Acquisition Costs and Value of Business Acquired (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance			$ 520.4	$ 396.5
Deferrals of commissions and expenses			56.5	56.0
Amortization:
Amortization			(71.8)	(85.9)
Interest accrued			31.1	27.1
Net amortization included in the Consolidated Statements of Operations			(40.7)	(58.8)
Change due to unrealized capital gains/losses on available-for-sale securities			(185.9)	70.2
Ending balance	$ 350.3	$ 463.9	350.3	463.9
Movement Analysis Of Value of Business Acquired VOBA [Roll Forward]
Beginning balance			708.7	526.8
Deferrals of commissions and expenses			4.1	4.4
Amortization			(115.2)	(99.6)
Interest accrued			39.6	42.3
Net amortization included in the Condensed Consolidated Statements of Operations			(75.6)	(57.3)
Change due to unrealized capital gains/losses on available-for-sale securities			(262.3)	154.0
Ending balance	374.9	627.9	374.9	627.9
Movement Analysis of Deferred Policy Acquisition Costs and Value of Business Acquired (VOBA) [Roll Forward]
Beginning balance			1,229.1	923.3
Deferrals of commissions and expenses			60.6	60.4
Amortization			(187.0)	(185.5)
Interest accrued			70.7	69.4
Net amortization included in the Condensed Consolidated Statements of Operations	(119.5)	(64.0)	(116.3)	(116.1)
Change due to unrealized capital gains/losses on available-for-sale securities			(448.2)	224.2
Ending balance	$ 725.2	$ 1,091.8	$ 725.2	$ 1,091.8
Minimum
Movement Analysis of Deferred Policy Acquisition Costs and Value of Business Acquired (VOBA) [Roll Forward]
Value of Business Acquired (VOBA), Interest accrued percentage			5.50%	5.50%
Maximum
Movement Analysis of Deferred Policy Acquisition Costs and Value of Business Acquired (VOBA) [Roll Forward]
Value of Business Acquired (VOBA), Interest accrued percentage			7.00%	7.00%