Securities (Summary of Investments) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale debt securities, amortized cost	$ 1,049,044	$ 881,570
Available for sale debt securities, unrealized gains	9,601	15,570
Available for sale debt securities, unrealized losses	12,812	2,569
Available for sale debt securities, allowance for credit losses	0	0
Available for sale debt securities, fair value	1,045,833	894,571
Obligations of U.S. government-sponsored enterprises [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale debt securities, amortized cost	181,044	131,186
Available for sale debt securities, unrealized gains	63	628
Available for sale debt securities, unrealized losses	2,502	145
Available for sale debt securities, allowance for credit losses	0	0
Available for sale debt securities, fair value	178,605	131,669
Mortgage-backed securities issued by U.S. government-sponsored agencies and U.S. government-sponsored enterprises [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale debt securities, amortized cost	843,485	725,890
Available for sale debt securities, unrealized gains	9,532	14,942
Available for sale debt securities, unrealized losses	9,315	527
Available for sale debt securities, allowance for credit losses	0	0
Available for sale debt securities, fair value	843,702	740,305
Individual name issuer trust preferred debt securities
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale debt securities, amortized cost	11,363	13,341
Available for sale debt securities, unrealized gains	6	0
Available for sale debt securities, unrealized losses	213	672
Available for sale debt securities, allowance for credit losses	0	0
Available for sale debt securities, fair value	11,156	12,669
Corporate bonds [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale debt securities, amortized cost	13,152	11,153
Available for sale debt securities, unrealized gains	0	0
Available for sale debt securities, unrealized losses	782	1,225
Available for sale debt securities, allowance for credit losses	0	0
Available for sale debt securities, fair value	$ 12,370	$ 9,928

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on 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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