Investments (Details 5) (USD $) In Millions	6 Months Ended
	Jun. 30, 2010	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Mar. 31, 2010
Changes in credit loss impairments on fixed maturities
Beginning balance	$ 4.5	$ 10.8	$ 10.8	$ 10.8	$ 10.8
New securities subject to credit impairment losses	6.3
Closing balance	$ 10.8	$ 10.8	$ 10.8	$ 10.8	$ 10.8