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Securities (Other-Than-Temporary Impairment) (Details) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2019 USD ($) security | Sep. 30, 2018 USD ($) | Sep. 30, 2019 USD ($) security | Sep. 30, 2018 USD ($) | Dec. 31, 2018 security
Other Than Temporary Impairment Credit Losses Recognized in Earnings |  |  |  |  |
Number of available-for-sale debt securities in an unrealized loss position | 70 |  | 70 |  | 184
Investment securities available-for-sale |  |  |  |  |
Other Than Temporary Impairment Credit Losses Recognized in Earnings |  |  |  |  |
OTTI credit losses | $ | $ 0 | $ 0 | $ 0 | $ 0 |
Foreign bonds |  |  |  |  |
Other Than Temporary Impairment Credit Losses Recognized in Earnings |  |  |  |  |
Number of available-for-sale debt securities in an unrealized loss position | 6 |  | 6 |  | 16
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities |  |  |  |  |
Other Than Temporary Impairment Credit Losses Recognized in Earnings |  |  |  |  |
Number of available-for-sale debt securities in an unrealized loss position | 37 |  | 37 |  | 108
U.S. Treasury securities |  |  |  |  |
Other Than Temporary Impairment Credit Losses Recognized in Earnings |  |  |  |  |
Number of available-for-sale debt securities in an unrealized loss position | 10 |  | 10 |  | 19

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