Summary of Investments - SOI Fixed Maturity AFS aging (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Amortized cost
Maturing in one year or less	$ 658,867
Maturing after one year through five years	3,603,240
Maturing after five years through ten years	4,427,116
Maturing after ten years	5,245,378
Mortgage-backed and asset-backed securities	3,068,107
Total fixed maturities	17,002,708	18,953,144
Estimated fair value
Maturing in one year or less	689,902
Maturing after one year through five years	3,922,438
Maturing after five years through ten years	4,729,717
Maturing after ten years	5,739,031
Mortgage-backed and asset-backed securities	3,286,579
Total fixed maturities	$ 18,367,667	$ 20,162,078