Investments (Amortized Cost and Fair Value of Fixed Maturities by Contractual Maturities) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Available For Sale Securities Debt Maturities Amortized Cost
Due in one year or less	$ 1,538,152
Due after one year through five years	8,318,044
Due after five year through ten years	9,485,912
Due after ten years	18,650,300
Asset and mortgage-backed securities	6,868,033
Total	44,860,441	$ 38,882,168
Available For Sale Securities Debt Maturities Fair Value
Due in one year or less	1,547,966
Due after one year through five years	8,656,979
Due after five year through ten years	10,275,538
Due after ten years	21,956,089
Asset and mortgage-backed securities	7,044,695
Total	$ 49,481,267	$ 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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