Summary of Significant Accounting Policies - Impact of ASC 326 (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	$ 977,414		$ 917,377
Allowance for credit losses on held-to-maturity debt securities	6
Ending balance	228,804		47,576	$ 39,539
Total Commercial | Commercial and industrial(1)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance	150,875		22,849	14,211
Total Commercial | Owner-occupied commercial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance	9,615		4,616	5,057
Total Commercial | Commercial mortgages
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance	31,071		7,452	6,806
Total Commercial | Construction
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance	12,190		3,891	3,712
Residential
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance	6,893		1,381	1,428
Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance	18,160		7,387	$ 8,325
State and political subdivisions
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on held-to-maturity debt securities	$ 6		0
Cumulative change in accounting principle (Note 2)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance			35,855
Cumulative change in accounting principle (Note 2) | Total Commercial | Commercial and industrial(1)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance			19,747
Cumulative change in accounting principle (Note 2) | Total Commercial | Owner-occupied commercial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance			(1,472)
Cumulative change in accounting principle (Note 2) | Total Commercial | Commercial mortgages
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance			1,662
Cumulative change in accounting principle (Note 2) | Total Commercial | Construction
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance			681
Cumulative change in accounting principle (Note 2) | Residential
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance			7,522
Cumulative change in accounting principle (Note 2) | Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance			7,715
Cumulative change in accounting principle (Note 2) | State and political subdivisions
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on held-to-maturity debt securities			$ 8
ASC 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on held-to-maturity debt securities		$ 0
Ending balance		(47,576)
Deferred tax assets		9,991
Allowance for credit losses on unfunded lending commitments		(1,547)
ASC 326 | Total Commercial | Commercial and industrial(1)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance		(22,849)
ASC 326 | Total Commercial | Owner-occupied commercial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance		(4,616)
ASC 326 | Total Commercial | Commercial mortgages
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance		(7,452)
ASC 326 | Total Commercial | Construction
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance		(3,891)
ASC 326 | Residential
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance		(1,381)
ASC 326 | Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance		(7,387)
ASC 326 | State and political subdivisions
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on held-to-maturity debt securities		0
ASC 326 | Balance, January 1, 2020 (as adjusted for change in accounting principle)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings		30,400
Allowance for credit losses on held-to-maturity debt securities		(8)
Ending balance		(83,431)
Deferred tax assets		18,452
Allowance for credit losses on unfunded lending commitments		(4,513)
ASC 326 | Balance, January 1, 2020 (as adjusted for change in accounting principle) | Total Commercial | Commercial and industrial(1)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance		(42,596)
ASC 326 | Balance, January 1, 2020 (as adjusted for change in accounting principle) | Total Commercial | Owner-occupied commercial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance		(3,144)
ASC 326 | Balance, January 1, 2020 (as adjusted for change in accounting principle) | Total Commercial | Commercial mortgages
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance		(9,114)
ASC 326 | Balance, January 1, 2020 (as adjusted for change in accounting principle) | Total Commercial | Construction
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance		(4,572)
ASC 326 | Balance, January 1, 2020 (as adjusted for change in accounting principle) | Residential
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance		(8,903)
ASC 326 | Balance, January 1, 2020 (as adjusted for change in accounting principle) | Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance		(15,102)
ASC 326 | Balance, January 1, 2020 (as adjusted for change in accounting principle) | State and political subdivisions
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on held-to-maturity debt securities		(8)
ASC 326 | Cumulative change in accounting principle (Note 2)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings		30,368
Allowance for credit losses on held-to-maturity debt securities		(8)
Ending balance		(35,855)
Deferred tax assets		8,461
Allowance for credit losses on unfunded lending commitments		(2,966)
ASC 326 | Cumulative change in accounting principle (Note 2) | Total Commercial | Commercial and industrial(1)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance		(19,747)
ASC 326 | Cumulative change in accounting principle (Note 2) | Total Commercial | Owner-occupied commercial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance		1,472
ASC 326 | Cumulative change in accounting principle (Note 2) | Total Commercial | Commercial mortgages
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance		(1,662)
ASC 326 | Cumulative change in accounting principle (Note 2) | Total Commercial | Construction
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance		(681)
ASC 326 | Cumulative change in accounting principle (Note 2) | Residential
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance		(7,522)
ASC 326 | Cumulative change in accounting principle (Note 2) | Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ending balance		(7,715)
ASC 326 | Cumulative change in accounting principle (Note 2) | State and political subdivisions
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on held-to-maturity debt securities		$ (8)