Debt - Interest Paid on Debt (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Interest Paid	$ 45.7	$ 37.7	$ 39.3
Senior Notes [Member] | Senior Notes, 6% Due November 30, 2015 [Member]
Debt Instrument [Line Items]
Interest Paid	15.0	15.0	15.0
Senior Notes [Member] | Senior Notes, 6% Due May 15, 2017 [Member]
Debt Instrument [Line Items]
Interest Paid	21.6	21.6	21.6
Subordinated Debt [Member] | Subordinated Debenture, 7.375 Percent Due 2054 [Member]
Debt Instrument [Line Items]
Interest Paid	8.5	0	0
Mortgage Note Payable [Member]
Debt Instrument [Line Items]
Interest Paid	0	0.3	0.4
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Interest Paid	$ 0.6	$ 0.8	$ 2.3