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Investment Securities - Schedule of Unrealized Losses and Estimated Fair Values (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
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Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items] |  |
Estimated Fair Value, Less Than 12 Months | $ 3,755 | $ 166,470
Available For Sale Securities Continuous Unrealized Income Loss Position Less Than Twelve Months Aggregate Gain Losses | (10) | (637)
Estimated Fair Value, 12 Months or More | 0 | 235,380
SecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLosses | 0 | (2,950)
Securities Continuous Unrealized Loss Position Fair Value | 3,755 | 401,850
SecuritiesContinuousUnrealizedLossPositionAggregateLosses | (10) | (3,587)
Mortgage - Backed Securities - Residential [Member] | Obligations of U.S. Government-Sponsored Enterprises [Member] |  |
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items] |  |
Estimated Fair Value, Less Than 12 Months | 3,755 | 111,969
Available For Sale Securities Continuous Unrealized Income Loss Position Less Than Twelve Months Aggregate Gain Losses | (10) | (436)
Estimated Fair Value, 12 Months or More | 0 | 219,015
SecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLosses | 0 | (2,801)
Securities Continuous Unrealized Loss Position Fair Value | 3,755 | 330,984
SecuritiesContinuousUnrealizedLossPositionAggregateLosses | $ (10) | (3,237)
Mortgage - Backed Securities - Commercial [Member] | Obligations of U.S. Government [Member] |  |
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items] |  |
Estimated Fair Value, Less Than 12 Months |  | 54,501
Available For Sale Securities Continuous Unrealized Income Loss Position Less Than Twelve Months Aggregate Gain Losses |  | (201)
Estimated Fair Value, 12 Months or More |  | 16,365
SecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLosses |  | (149)
Securities Continuous Unrealized Loss Position Fair Value |  | 70,866
SecuritiesContinuousUnrealizedLossPositionAggregateLosses |  | $ (350)

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