Fair Values of Financial Instruments, Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financial assets [Abstract]
HTM securities	$ 641,262	$ 778,675
Carrying Amount [Member] | Level 2 [Member]
Financial assets [Abstract]
HTM securities	630,074	783,599
Financial liabilities: [Abstract]
Time deposits	861,193	930,678
Long-term debt	64,211	73,724
Junior subordinated debt	101,196	101,196
Carrying Amount [Member] | Level 3 [Member]
Financial assets [Abstract]
Net Loans	7,074,864	6,822,147
Estimated Fair Value [Member] | Level 2 [Member]
Financial assets [Abstract]
HTM securities	641,262	778,675
Financial liabilities: [Abstract]
Time deposits	858,085	920,534
Long-term debt	64,373	73,927
Junior subordinated debt	105,694	100,114
Estimated Fair Value [Member] | Level 3 [Member]
Financial assets [Abstract]
Net Loans	$ 6,999,690	$ 6,754,460