Investments (Fixed Maturity Securities Pledged And Received As Collateral) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 24,216,876	$ 24,006,407
Available-for-sale Securities	25,077,338	23,982,119
Collateral Fixed Maturity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	74,647	80,891
Available-for-sale Securities	77,806	83,950
Collateral Received Fixed Maturity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities	668,046	616,584
Reported Value Measurement [Member]
Debt Securities, Available-for-sale [Line Items]
Assets Held-in-trust	20,635,739	20,072,735
Estimate of Fair Value Measurement [Member]
Debt Securities, Available-for-sale [Line Items]
Assets Held-in-trust	$ 21,609,979	$ 20,366,170

The total amount of cash and securities held by third party trustees pursuant to terms of debt instruments or other agreements as of the date of each statement of financial position presented, which can be used by the trustee only to pay the noncurrent portion of specified obligations.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(b))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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+ References

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