Investments (Details 14) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 item	Dec. 31, 2011 item
Mortgage Loan Modifications
Number of mortgage loans modified as a troubled debt restructuring	338	159
Recorded investment of mortgage loans modified as a troubled debt restructuring	$ 35.1	$ 13.9
Number of mortgage loans modified as a troubled debt restructuring in payment default	13	8
Recorded investment of mortgage loans modified as a troubled debt restructuring in payment default	13.7	4.7
Brick and mortar
Mortgage Loan Modifications
Number of mortgage loans modified as a troubled debt restructuring	2	1
Recorded investment of mortgage loans modified as a troubled debt restructuring	18.0	4.4
Number of mortgage loans modified as a troubled debt restructuring in payment default	1	1
Recorded investment of mortgage loans modified as a troubled debt restructuring in payment default	13.7	4.4
Home equity
Mortgage Loan Modifications
Number of mortgage loans modified as a troubled debt restructuring	324	151
Recorded investment of mortgage loans modified as a troubled debt restructuring	15.0	7.9
Number of mortgage loans modified as a troubled debt restructuring in payment default	12	6
First liens
Mortgage Loan Modifications
Number of mortgage loans modified as a troubled debt restructuring	12	7
Recorded investment of mortgage loans modified as a troubled debt restructuring	2.1	1.6
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