Investments (Details 9) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Gross unrealized losses with number of securities [Line Items]
Available For Sale Securities Gross Unrealized Losses	$ 214,352	$ 292,486
Percentage Of Total Gross Unrealized Losses For Fixed Maturity And Equity Securities	100.00%	100.00%
Less Than 20 Percent [Member]
Gross unrealized losses with number of securities [Line Items]
Available For Sale Securities Gross Unrealized Losses	92,037	131,155
Percentage Of Total Gross Unrealized Losses For Fixed Maturity And Equity Securities	42.90%	44.80%
More Than Or Equal To 20 Percent For Less Than Six Months [Member]
Gross unrealized losses with number of securities [Line Items]
Available For Sale Securities Gross Unrealized Losses	9,986	51,503
Percentage Of Total Gross Unrealized Losses For Fixed Maturity And Equity Securities	4.70%	17.60%
More Than Or Equal To 20 Percent For Six Months Or Greater [Member]
Gross unrealized losses with number of securities [Line Items]
Available For Sale Securities Gross Unrealized Losses	$ 112,329	$ 109,828
Percentage Of Total Gross Unrealized Losses For Fixed Maturity And Equity Securities	52.40%	37.60%