Fair Value of Financial Instruments (Details) (Fair Value Inputs Level2 [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Market Approach Valuation Technique [Member] | Junior Subordinated Debt [Member]
Financial Instruments Not Measured at Fair Value
Market interest rate (as a percent)	6.15%	6.84%
Market Approach Valuation Technique [Member] | Mortgages [Member] | Minimum [Member]
Financial Instruments Not Measured at Fair Value
Market interest rate (as a percent)	2.79%	2.42%
Market Approach Valuation Technique [Member] | Mortgages [Member] | Maximum [Member]
Financial Instruments Not Measured at Fair Value
Market interest rate (as a percent)	8.79%	9.58%
Estimate of Fair Value Measurement [Member] | Junior Subordinated Debt [Member]
Financial Instruments Not Measured at Fair Value
Estimated fair value lower than carrying value	21.0	24.3
Estimate of Fair Value Measurement [Member] | Mortgages [Member]
Financial Instruments Not Measured at Fair Value
Estimated fair value lower than carrying value	7.0	12.0