Investments Textuals (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Fixed Maturity Securities [Member]	Dec. 31, 2011 Fixed Maturity Securities [Member]	Jun. 30, 2012 Equity Securities [Member]	Dec. 31, 2011 Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Other-than-temporary impairments, minimum percentage decline	20.00%		20.00%
Realized investment gains losses from impairment	$ 0	$ 8.0	$ 0	$ 8.0
Securities in unrealized loss positions, number of positions					95	131	3	6
Percentage of securities in unrealized loss position					5.20%	7.10%	7.10%	14.30%
Number of securities in continuous unrealized loss position for more than 12 months					5	4	1	1