Mergers and acquisitions - Farmers National Bank Narrative (Details) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
	Feb. 14, 2020 USD ($) branch $ / shares shares	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)
Business Acquisition [Line Items]
Assets assumed in acquisition		$ 7,255,536	$ 5,940,402	$ 7,255,536	$ 5,940,402		$ 6,124,921
Loans assumed in acquisition		4,827,023		4,827,023		$ 4,409,642	4,409,642
Deposits assumed in acquisition		5,952,801		5,952,801			$ 4,934,938
Goodwill resulting from merger				6,390	31,396
Merger related expenses		1,586	$ 3,783	4,636	$ 4,404
Farmers National
Business Acquisition [Line Items]
Number of branches acquired | branch	5
Assets assumed in acquisition	$ 258,218
Loans assumed in acquisition	182,171
Deposits assumed in acquisition	$ 209,535
Business acquisition, shares issued (in shares) | shares	954,797
Cash consideration	$ 15,001
Business acquisition, share price (dollar per share) | $ / shares	$ 36.70
Business combination, consideration, value	$ 50,042
Goodwill resulting from merger	$ 6,390
Merger related expenses		$ 1,503		$ 2,097