Income Taxes (Details 2) - USD ($)		12 Months Ended
	Dec. 22, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reasons for the difference between income tax expense and statutory federal income tax
Statutory federal income tax		$ 22,332,000	$ 25,232,000	$ 22,056,000
Tax-exempt interest income		(439,000)	(552,000)	(650,000)
State taxes, net of federal income tax benefit		3,424,000	4,064,000	3,315,000
Deferred tax liability remeasurement		0	0	(875,000)	$ 2,610,000
Other		(437,000)	(605,000)	(1,233,000)
Total provision		$ 24,880,000	$ 28,139,000	$ 22,613,000
Reasons for the difference between income tax expense rate and statutory federal income tax rate
Statutory federal income tax (as a percent)	21.00%	21.00%	21.00%	21.00%	35.00%
Tax-exempt interest income (as a percent)		(0.40%)	(0.50%)	(0.60%)
State taxes, net of federal income tax benefit (as a percent)		3.20%	3.40%	3.20%
Deferred tax liability remeasurement (as a percent)		0.00%	0.00%	(0.80%)
Other (as a percent)		(0.40%)	(0.50%)	(1.30%)
Total income tax expense (benefit) (as a percent)		23.40%	23.40%	21.50%
Deferred tax assets:
Reserve for loan and lease losses		$ 35,696,000	$ 28,792,000
Deferred Tax Assets, Tax Credit Carryforwards, Other		8,606,000	0
Operating lease liability		5,704,000	5,899,000
Accruals for employee benefits		2,963,000	2,842,000
Capitalized loan costs		893,000	0
Mortgage servicing		173,000	0
Other		678,000	222,000
Total deferred tax assets		54,713,000	37,755,000
Deferred tax liabilities:
Differing depreciable bases in premises and leased equipment		13,118,000	18,614,000
Right of use assets - leases		5,737,000	5,899,000
Differing bases in assets related to acquisitions		4,160,000	4,092,000
Tax advantaged partnerships		3,770,000	4,383,000
Net unrealized gains on securities available-for-sale		5,827,000	1,640,000
Mortgage servicing		0	394,000
Capitalized loan costs		0	1,207,000
Prepaid expenses		334,000	297,000
Other		300,000	544,000
Total deferred tax liabilities		33,246,000	37,070,000
Deferred Tax Assets, Net, Total		21,467,000	685,000
Reconciliation of the beginning and ending amounts of unrecognized tax benefits
Balance, at beginning of the period		0	0	$ 1,112,000
Additions based on tax positions related to the current year		0	0	0
Additions for tax positions of prior years		0	0	0
Reductions for tax positions of prior years		0	0	0
Reductions due to lapse in statute of limitations		0	0	0
Settlements		0	0	(1,112,000)
Balance at end of the period		0	0	0	$ 1,112,000
Valuation allowance for deferred tax assets		0	0
Unrecognized tax benefits that would affect the effective tax rate if recognized		0	0	0
Interest and penalties net of tax recognized		0.00	0.00	(90,000.00)
Accrued interest and penalties		0	0	0
Investment securities available-for-sale
Reasons for the difference between income tax expense and statutory federal income tax
Total provision		$ 67,000	$ 0	$ (83,000)