Investments - Mortgage Loan Modifications (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($) item	Jun. 30, 2015 USD ($) item	Jun. 30, 2016 USD ($) item	Jun. 30, 2015 USD ($) item
Mortgage Loan Modifications
Number of mortgage loans modified as a troubled debt restructuring	2	4	4	12
Recorded investment of mortgage loans modified as a troubled debt restructuring | $	$ 0.2	$ 0.2	$ 0.4	$ 0.7
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	1	4	3	12
Recorded investment of mortgage loans modified as a troubled debt restructuring | $		$ 0.2	$ 0.2	$ 0.7
Number of mortgage loans modified as a troubled debt restructuring in payment default				1
First liens
Mortgage Loan Modifications
Number of mortgage loans modified as a troubled debt restructuring	1		1
Recorded investment of mortgage loans modified as a troubled debt restructuring | $	$ 0.2		$ 0.2