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SECURITIES - Additional Information (Details) - USD ($) $ in Billions | 3 Months Ended
--- | ---
Mar. 31, 2020 | Mar. 31, 2019
Investments, Debt and Equity Securities [Abstract] |  |
Residential Investment securities sold, carrying value | $ 41.9 | $ 10.5

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- Definition Carrying value of mortgage backed securities sold during period. + References No definition available. + Details
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Namespace Prefix: | nly_
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Balance Type: | debit
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- References No definition available. + Details
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