Securities, Amortized Cost and Fair Value of Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Available-for-sale, amortized cost [Abstract]
Due in one year or less	$ 1,330
Due after one through five years	92,173
Due after five through ten years	167,212
Due after ten years	164,029
Amortized cost	1,150,224	$ 978,774
Available for sale, fair value [Abstract]
Due in one year or less	1,334
Due after one through five years	92,176
Due after five through ten years	166,553
Due after ten years	163,673
Fair value	1,155,195	997,261
U.S. Government Sponsored Agency Mortgage-backed Securities [Member]
Available-for-sale, amortized cost [Abstract]
Without single maturity date	669,134
Amortized cost	669,134	640,537
Available for sale, fair value [Abstract]
Without single maturity date	674,832
Fair value	674,832	651,807
Other Debt Securities [Member]
Available-for-sale, amortized cost [Abstract]
Without single maturity date	56,346
Amortized cost	56,346	56,443
Available for sale, fair value [Abstract]
Without single maturity date	56,627
Fair value	$ 56,627	$ 56,245

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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