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Investments - AFS Securities with Cost Basis in Excess of Fair Value - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Investments Debt And Equity Securities [Abstract]
Available for sale securities with cost basis in excess of fair value cost basis	$ 1,239.6	$ 529.2

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- Definition

Available for sale securities with cost basis in excess of fair value cost basis.

+ References

No definition available.

+ Details

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Period Type:	instant

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- References

No definition available.

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