Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 Integer		Dec. 31, 2012	Dec. 31, 2011
Number of Operating Segments	3
Policy Loans	$ 3,276.0	[1]	$ 3,133.8
Accumulated Depreciation for Property and Equipment	760.8		705.0
Value of Business Acquired	19.0		23.5
Accumulated Amortization of Value of Business Acquired	138.2		131.5
Amortization of Value of Business Acquired	4.5		7.5	7.4
Deferred Gain on Reinsurance	53.6		67.4
Premium tax expense	137.0		136.0	134.9
Assets, Participation Fund Account (PFA)	$ 339.2		$ 380.4

[1] (1)The amortized cost for fixed maturity securities and mortgage loans represents original cost reduced by repayments, write-downs from other-than-temporary declines in fair value, amortization of premiums, and/or accretion of discounts.