Investments - Mortgage Loan Modifications (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) item	Mar. 31, 2015 USD ($) item
Mortgage Loan Modifications
Number of mortgage loans modified as a troubled debt restructuring	2	8
Recorded investment of mortgage loans modified as a troubled debt restructuring | $	$ 0.2	$ 0.5
Number of mortgage loans modified as a troubled debt restructuring in payment default		1
Home equity
Mortgage Loan Modifications
Number of mortgage loans modified as a troubled debt restructuring	2	8
Recorded investment of mortgage loans modified as a troubled debt restructuring | $	$ 0.2	$ 0.5
Number of mortgage loans modified as a troubled debt restructuring in payment default		1