Deferred Policy Acquisition Costs and Value of Business Acquired (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	$ 4,316.1		$ 3,221.6
Deferrals of commissions and expenses	91.6		104.5
Amortization:
Amortization	(159.6)		(174.8)
Interest accrued	58.3	[1]	58.4	[1]
Net amortization included in the Consolidated Statements of Operations	(101.3)		(116.4)
Change in unrealized capital gains/losses on available-for-sale securities	(293.3)		262.0
Ending balance	4,013.1		3,471.7
Movement Analysis Of Value of Business Acquired VOBA [Roll Forward]
Beginning balance	1,035.5		434.7
Deferrals of commissions and expenses	3.4		3.3
Amortization:
Amortization	(47.3)		(36.6)
Interest accrued	22.5	[1]	22.5	[1]
Net amortization included in Condensed Consolidated Statements of Operations	(24.8)		(14.1)
Change in unrealized capital gains/losses on available-for-sale securities	(166.4)		124.0
Ending balance	847.7		547.9
Movement Analysis of Deferred Policy Acquisition Costs and Value of Business Acquired (VOBA) [Roll Forward]
Beginning balance	5,351.6		3,656.3
Deferrals of commissions and expenses	95.0		107.8
Amortization:
Amortization	(206.9)		(211.4)
Interest accrued	80.8	[1]	80.9	[1]
Net amortization included in Condensed Consolidated Statements of Operations	(126.1)		(130.5)
Change in unrealized capital gains/losses on available-for-sale securities	(459.7)		386.0
Ending balance	$ 4,860.8		$ 4,019.6
Minimum
Amortization:
Deferred Policy Acquisition Costs, Interest accrued percentage	0.60%		1.70%
Value of Business Acquired (VOBA), Interest accrued percentage	4.10%		3.00%
Maximum
Amortization:
Deferred Policy Acquisition Costs, Interest accrued percentage	7.40%		7.40%
Value of Business Acquired (VOBA), Interest accrued percentage	7.50%		7.50%

[1] Interest accrued at the following rates for DAC: 0.6% to 7.4% during 2014 and 1.7% to 7.4% during 2013. Interest accrued at the following rates for VOBA: 4.1% to 7.5% during 2014 and 3.0% to 7.5% during 2013.