Schedule 2 - Parent Company Financial Statements - Balance Sheets (Parenthetical) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Amortized Cost of Fixed Maturity Securities	$ 4,341.7	$ 4,370.5
Fair Value of Notes Payable	804.4us-gaap_NotesPayableFairValueDisclosure	667.1us-gaap_NotesPayableFairValueDisclosure
Senior Notes [Member] \| Senior Notes Payable, 6.00% due 2017 [Member]
Senior Notes Payable, Interest Rate	6.00%
Senior Notes [Member] \| Senior Notes Payable, 6.00% due 2015 [Member]
Senior Notes Payable, Interest Rate	6.00%
Subordinated Debt [Member] \| Subordinated Debenture, 7.375 Percent Due 2054 [Member]
Senior Notes Payable, Interest Rate	7.375%
Parent Company [Member]
Amortized Cost of Fixed Maturity Securities	12.2	0
Equity Securities at Cost	21.9	4.7
Parent Company [Member] \| Senior Notes [Member] \| Senior Notes Payable, 6.00% due 2017 [Member]
Fair Value of Notes Payable	390.2	395.5
Senior Notes Payable, Interest Rate	6.00%	6.00%
Parent Company [Member] \| Senior Notes [Member] \| Senior Notes Payable, 6.00% due 2015 [Member]
Fair Value of Notes Payable	260.2	271.6
Senior Notes Payable, Interest Rate	6.00%	6.00%
Parent Company [Member] \| Subordinated Debt [Member] \| Subordinated Debenture, 7.375 Percent Due 2054 [Member]
Fair Value of Notes Payable	$ 154.0

Equity securities at cost, including available-for sale and trading equity securities

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Contractual interest rate for funds borrowed, under the debt agreement.

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Fair value portion of notes payable.

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