Fair Value of Financial Instruments - Carrying Amounts and Fair Values (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Level 3 | Policy Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	$ 67.5	$ 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	3,164.1	2,762.8
Fair Value	3,165.3	2,763.8
Level 1 | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	206.1	181.0
Fair Value	206.1	181.0
Reported Value Measurement | Surplus Notes | Level 3 | Surplus Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Surplus notes	$ 30.0	$ 30.0