SOI Fixed Maturity AFS maturity aging (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Amortized cost
Maturing in one year or less	$ 668,305
Maturing after one year through five years	3,741,043
Maturing after five years through ten years	6,570,148
Maturing after ten years	5,088,280
Mortgage-backed and asset-backed securities	5,604,951
Total fixed maturities	21,672,727	$ 20,007,462
Estimated fair value
Maturing in one year or less	690,369
Maturing after one year through five years	3,917,479
Maturing after five years through ten years	6,650,854
Maturing after ten years	5,208,071
Mortgage-backed and asset-backed securities	5,686,930
Total fixed maturities	$ 22,153,703	$ 20,531,627