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Investments (Exposure To Concentrations Of Credit Risk) (Details) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2020 | Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items] |  |
Document Period End Date | Mar. 31, 2020 |
Government Of Japan [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | $ 1,660 | $ 813
Available-for-sale Securities | 1,672 | 852
Canadian Province Of Quebec Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 1,132 | 1,205
Available-for-sale Securities | 1,986 | 2,163
Canadian Province Of Ontario Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 941 | 1,014
Available-for-sale Securities | $ 1,289 | $ 1,379

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- Definition The end date of the period reflected on the cover page if a periodic report. For all other reports and registration statements containing historical data, it is the date up through which that historical data is presented. If there is no historical data in the report, use the filing date. The format of the date is CCYY-MM-DD. + References No definition available. + Details
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- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References No definition available. + Details
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