Fair Value Measurements and Fair Value of Financial Instruments, Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financial assets [Abstract]
HTM securities	$ 689,129	$ 636,827
Carrying Amount [Member] | Level 1 [Member]
Financial liabilities [Abstract]
Subordinated debt	100,000	100,000
Carrying Amount [Member] | Level 2 [Member]
Financial assets [Abstract]
HTM securities	683,103	616,560
Financial liabilities [Abstract]
Time deposits	552,273	633,479
Long-term debt	14,020	39,097
Junior subordinated debt	101,196	101,196
Carrying Amount [Member] | Level 3 [Member]
Financial assets [Abstract]
Net loans	7,474,466	7,390,004
Estimated Fair Value [Member] | Level 1 [Member]
Financial liabilities [Abstract]
Subordinated debt	107,684	103,277
Estimated Fair Value [Member] | Level 2 [Member]
Financial assets [Abstract]
HTM securities	689,129	636,827
Financial liabilities [Abstract]
Time deposits	553,125	638,721
Long-term debt	14,376	39,820
Junior subordinated debt	109,001	108,926
Estimated Fair Value [Member] | Level 3 [Member]
Financial assets [Abstract]
Net loans	$ 7,615,405	$ 7,530,033