Reclassification Adjustments Out of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Reclassification Adjustment out of AOCI [Abstract]
Net securities (gains) losses	$ (179)	$ 467
Interest income (expense)	80,348	79,055
Other noninterest expense	3,119	2,757
Income tax (benefit)	11,142	11,155
Net income	39,126	39,846
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of AOCI [Abstract]
Total reclassifications during the period, net of tax	241	368
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of AOCI [Abstract]
Income tax (benefit)	(35)	(35)
Net income	102	107
Amortization of Unrealized Gains Related to Securities Transfer [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of AOCI [Abstract]
Interest income (expense)	137	142
Net Unrealized Losses on Cash Flow Hedges Reclassified to Interest Expense [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of AOCI [Abstract]
Interest income (expense)	0	21
Income tax (benefit)	0	(5)
Net income	0	16
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of AOCI [Abstract]
Income tax (benefit)	(47)	(81)
Net income	139	245
Amortization of Net Losses [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of AOCI [Abstract]
Other noninterest expense	157	298
Amortization of Prior Service Costs [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of AOCI [Abstract]
Other noninterest expense	$ 29	$ 28