Investments (Details) - Investment Fund Consolidation (USD $)	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010
Investment Fund Consolidation [Line Items]
Fixed maturities, at fair value	$ 26,242,802,000	$ 26,190,025,000
Cost or Amortized cost of Fixed maturities	25,442,779,000	25,771,715,000
Cash and cash equivalents	3,311,146,000	3,825,125,000	2,859,342,000	3,022,868,000
Other liabilities	793,940,000	770,945,000
Non-controlling interest in equity of consolidated subsidiaries	1,345,993,000	1,344,472,000
Five Oaks Investment Corp [Member]
Investment Fund Consolidation [Line Items]
Investment amount	25,000,000
Percentage ownership	94.00%
Cash and cash equivalents	14,900,000
Other liabilities	69,100,000
Non-controlling interest in equity of consolidated subsidiaries	1,500,000
Securities pledged as collateral	75,600,000
Five Oaks Investment Corp [Member] | Maximum
Investment Fund Consolidation [Line Items]
Investment Fund Maximum Leverage Permitted	79,500,000
Five Oaks Investment Corp [Member] | Residential Mortgage Backed Securities Member
Investment Fund Consolidation [Line Items]
Fixed maturities, at fair value	80,700,000
Cost or Amortized cost of Fixed maturities	$ 80,600,000