Investments (Details 10)	Sep. 30, 2011	Dec. 31, 2010
NAIC 1 [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
NAIC ratings distribution of CMBS	94.30%	93.70%
NAIC 2 [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
NAIC ratings distribution of CMBS	4.10%	3.20%
NAIC 3 [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
NAIC ratings distribution of CMBS	0.50%	1.80%
NAIC 4 [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
NAIC ratings distribution of CMBS	0.70%	1.00%
NAIC 5 [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
NAIC ratings distribution of CMBS	0.00%	0.30%
NAIC 6 [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
NAIC ratings distribution of CMBS	0.40%	0.00%