Consolidated statements of changes in shareholders' equity - USD ($) $ in Thousands	Total	Period of adoption, adjustment	Period of adoption, adjusted balance	Common stock	Common stock Period of adoption, adjusted balance	Additional paid-in capital	Additional paid-in capital Period of adoption, adjusted balance	Retained earnings	Retained earnings Period of adoption, adjustment	Retained earnings Period of adoption, adjusted balance	Accumulated other comprehensive income, net	Accumulated other comprehensive income, net Period of adoption, adjusted balance
Balance at Dec. 31, 2018	$ 671,857	$ (1,309)	$ 670,548	$ 30,725	$ 30,725	$ 424,146	$ 424,146	$ 221,213	$ (1,309)	$ 219,904	$ (4,227)	$ (4,227)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	38,276							38,276
Other comprehensive income (loss), net of taxes	13,396										13,396
Stock based compensation expense	3,785			6		3,779
Restricted stock units vested and distributed, net of shares withheld	(2,510)			124		(2,634)
Shares issued under employee stock purchase program	364			11		353
Dividends declared	(5,100)							(5,100)
Balance at Jun. 30, 2019	718,759			30,866		425,644		253,080			9,169
Balance at Mar. 31, 2019	694,577			30,853		423,647		236,947			3,130
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	18,688							18,688
Other comprehensive income (loss), net of taxes	6,039										6,039
Stock based compensation expense	2,147			3		2,144
Restricted stock units vested and distributed, net of shares withheld	(137)			10		(147)
Dividends declared	(2,555)							(2,555)
Balance at Jun. 30, 2019	718,759			30,866		425,644		253,080			9,169
Balance at Dec. 31, 2019	762,329	$ (25,018)	$ 737,311	31,034	$ 31,034	425,633	$ 425,633	293,524	$ (25,018)	$ 268,506	12,138	$ 12,138
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	23,618							23,618
Other comprehensive income (loss), net of taxes	11,751										11,751
Common stock issued in connection with acquisition of FNB Financial Corp., net of registration costs	34,847			955		33,892
Stock based compensation expense	4,233			11		4,222
Restricted stock units vested and distributed, net of shares withheld	(1,162)			89		(1,251)
Shares issued under employee stock purchase program	446			12		434
Dividends declared	(5,828)							(5,828)
Balance at Jun. 30, 2020	805,216			32,101		462,930		286,296			23,889
Balance at Mar. 31, 2020	782,330			32,067		460,938		266,385			22,940
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	22,873							22,873
Other comprehensive income (loss), net of taxes	949										949
Stock based compensation expense	2,350			6		2,344
Restricted stock units vested and distributed, net of shares withheld	(324)			28		(352)
Dividends declared	(2,962)							(2,962)
Balance at Jun. 30, 2020	$ 805,216			$ 32,101		$ 462,930		$ 286,296			$ 23,889