Investments - Mortgage Loan Modifications (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) item	Dec. 31, 2014 USD ($) item	Dec. 31, 2013 USD ($) item
Mortgage Loan Modifications
Number of mortgage loans modified as a troubled debt restructuring	14	78	74
Recorded investment of mortgage loans modified as a troubled debt restructuring | $	$ 0.6	$ 8.2	$ 5.3
Number of mortgage loans modified as a troubled debt restructuring in payment default	2	4	20
Recorded investment of mortgage loans modified as a troubled debt restructuring in payment default | $		$ 0.7	$ 0.3
Brick and mortar
Mortgage Loan Modifications
Number of mortgage loans modified as a troubled debt restructuring		2	2
Recorded investment of mortgage loans modified as a troubled debt restructuring | $		$ 5.1	$ 0.9
Number of mortgage loans modified as a troubled debt restructuring in payment default		1
Recorded investment of mortgage loans modified as a troubled debt restructuring in payment default | $		$ 0.7
Home equity
Mortgage Loan Modifications
Number of mortgage loans modified as a troubled debt restructuring	14	75	69
Recorded investment of mortgage loans modified as a troubled debt restructuring | $	$ 0.6	$ 3.0	$ 3.8
Number of mortgage loans modified as a troubled debt restructuring in payment default	2	3	19
First liens
Mortgage Loan Modifications
Number of mortgage loans modified as a troubled debt restructuring		1	3
Recorded investment of mortgage loans modified as a troubled debt restructuring | $		$ 0.1	$ 0.6
Number of mortgage loans modified as a troubled debt restructuring in payment default			1
Recorded investment of mortgage loans modified as a troubled debt restructuring in payment default | $			$ 0.3