Investments (Details 13) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer	$ 2,312,167,000	$ 1,003,524,000
Mortgage Loans On Real Estate Due One Year Through Five Years [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer	1,187,387,000	493,027,000
Mortgage Loans On Real Estate Due After Five Years [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer	776,655,000	299,252,000
Mortgage Loans On Real Estate Due After Ten Years [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer	$ 348,125,000	$ 211,245,000