7. Investing Activities (Details 3) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair Value | Less than 12 months
U.S. government and agency
State and political subdivision	4.8	15.4
Foreign government		7.2
Corporate	49.9	113.4
Commercial mortgage-backed ("CMBS")		50.3
Residential mortgage-backed ("RMBS")	16.5	78.0
CDO/CLO	1.2	4.8
Other asset-backed	3.2	24.4
Total temporarily impaired securities	75.6	293.5
Below investment grade	15.3	25.3
Fair Value | Greater than 12 months
U.S. government and agency	3.5	3.5
State and political subdivision	1.0	0.9
Foreign government
Corporate	67.4	69.3
Commercial mortgage-backed ("CMBS")	13.1	6.9
Residential mortgage-backed ("RMBS")	73.0	91.1
CDO/CLO	42.4	40.6
Other asset-backed	10.7	16.5
Total temporarily impaired securities	211.1	228.8
Below investment grade	52.9	74.8
Fair Value | Total
U.S. government and agency	3.5	3.5
State and political subdivision	5.8	16.3
Foreign government		7.2
Corporate	117.3	182.7
Commercial mortgage-backed ("CMBS")	13.1	57.2
Residential mortgage-backed ("RMBS")	89.5	169.1
CDO/CLO	43.6	45.4
Other asset-backed	13.9	40.9
Total temporarily impaired securities	286.7	522.3
Below investment grade	68.2	100.1
Unrealized Losses | Less than 12 months
U.S. government and agency
State and political subdivision	(0.2)
Foreign government		(0.4)
Corporate	(1.5)	(3.5)
Commercial mortgage-backed ("CMBS")		(1.2)
Residential mortgage-backed ("RMBS")	(0.3)	(3.3)
CDO/CLO	(0.1)	(0.4)
Other asset-backed		(0.2)
Total temporarily impaired securities	(2.1)	(9.0)
Below investment grade	(1.5)	(1.6)
Number of securities	24	129
Unrealized Losses | Greater than 12 months
U.S. government and agency	(0.4)	(0.5)
State and political subdivision	(0.4)	(0.5)
Foreign government
Corporate	(25.2)	(34.0)
Commercial mortgage-backed ("CMBS")	(1.4)	(2.7)
Residential mortgage-backed ("RMBS")	(9.8)	(17.1)
CDO/CLO	(5.9)	(11.8)
Other asset-backed	(6.8)	(7.1)
Total temporarily impaired securities	(49.9)	(73.7)
Below investment grade	(29.0)	(50.2)
Number of securities	104	139
Unrealized Losses | Total
U.S. government and agency	(0.4)	(0.5)
State and political subdivision	(0.6)	(0.5)
Foreign government		(0.4)
Corporate	(26.7)	(37.5)
Commercial mortgage-backed ("CMBS")	(1.4)	(3.9)
Residential mortgage-backed ("RMBS")	(10.1)	(20.4)
CDO/CLO	(6.0)	(12.2)
Other asset-backed	(6.8)	(7.3)
Total temporarily impaired securities	(52.0)	(82.7)
Below investment grade	$ (30.5)	$ (51.8)
Number of securities	128	268