- SOI Fixed Maturity AFS maturity aging (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Amortized cost
Maturing in one year or less	$ 721,952
Maturing after one year through five years	3,775,332
Maturing after five years through ten years	7,894,918
Maturing after ten years	5,064,983
Mortgage-backed and asset-backed securities	5,305,777
Amortized cost	22,762,962	$ 21,672,727
Estimated fair value
Maturing in one year or less	735,235
Maturing after one year through five years	3,895,328
Maturing after five years through ten years	8,085,972
Maturing after ten years	5,455,996
Mortgage-backed and asset-backed securities	5,420,608
Total fixed maturities	$ 23,593,139	$ 22,153,703