Deferred Policy Acquisition Costs and Value of Business Acquired (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	$ 520.4	$ 396.5
Deferrals of commissions and expenses	18.3	18.7
Amortization:
Amortization	(9.4)	(28.3)
Interest accrued	9.3	9.0
Net amortization included in the Consolidated Statements of Operations	(0.1)	(19.3)
Change due to unrealized capital gains/losses on available-for-sale securities	(88.0)	35.7
Ending balance	450.6	360.2
Movement Analysis Of Value of Business Acquired VOBA [Roll Forward]
Beginning balance	708.7	526.8
Deferrals of commissions and expenses	1.4	1.5
Amortization	(11.4)	(17.4)
Interest accrued	13.5	14.2
Net amortization included in the Condensed Consolidated Statements of Operations	2.1	(3.2)
Change due to unrealized capital gains/losses on available-for-sale securities	(133.5)	44.1
Ending balance	578.7	481.0
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	19.7	20.2
Amortization	20.8	45.7
Interest accrued	22.8	23.2
Net amortization of deferred policy acquisition costs and value of business acquired	2.0	(22.5)
Change due to unrealized capital gains/losses on available-for-sale securities	(221.5)	79.8
Ending balance	$ 1,029.3	$ 841.2
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%