Fair Value of Financial Instruments - Fair Value by Balance Sheet Grouping (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Level 3 | Policy Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	$ 67.3	$ 66.1
Fair Value	66.9	65.6
Level 3 | Investment Contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	2,875.6	2,762.8
Fair Value	2,877.0	2,763.8
Level 1 | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	140.9	181.0
Fair Value	140.9	181.0
Reported Value Measurement | Surplus Note | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes Payable, Fair Value Disclosure	30.0	30.0
Estimate of Fair Value Measurement | Surplus Note | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes Payable, Fair Value Disclosure	$ 30.0	$ 30.0