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Commitments, Contingencies and Guarantees Commitments, Contingencies and Guarantees (Narrative) (Details) - USD ($) $ in Millions | Mar. 31, 2021 | Dec. 31, 2020
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Commitments and Contingencies Disclosure [Abstract] |  |
Liability For Expected Credit Losses Included in Other Liabilities | $ 1 | $ 2

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- Definition Liability For Expected Credit Losses Included in Other Liabilities, associated with unfunded commitments. + References No definition available. + Details
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Namespace Prefix: | rga_
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Balance Type: | credit
Period Type: | instant

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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | na
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