Investments (Amortized Cost and Fair Value of Fixed Maturities by Contractual Maturities) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Available For Sale Securities Debt Maturities Amortized Cost
Due in one year or less	$ 1,305,265
Due after one year through five years	8,823,728
Due after five year through ten years	9,519,138
Due after ten years	16,425,488
Asset and mortgage-backed securities	6,383,999
Total	42,457,618	$ 38,882,168
Available For Sale Securities Debt Maturities Fair Value
Due in one year or less	1,314,533
Due after one year through five years	9,130,980
Due after five year through ten years	10,171,840
Due after ten years	19,053,488
Asset and mortgage-backed securities	6,518,464
Total	$ 46,189,305	$ 39,992,346

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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