Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Cumulative adjustment for adoption of ASU 842	January 1, 2019, as adjusted	Common Stock	Common Stock January 1, 2019, as adjusted	Retained Earnings	Retained Earnings Cumulative adjustment for adoption of ASU 842	Retained Earnings January 1, 2019, as adjusted	Treasury Stock	Treasury Stock January 1, 2019, as adjusted	AOCI Attributable to Parent [Member]	AOCI Attributable to Parent [Member] January 1, 2019, as adjusted
Balance at beginning of period at Dec. 31, 2018	$ 623,739	$ 125	$ 623,864	$ 514,703	$ 514,703	$ 116,874	$ 125	$ 116,999	$ 0	$ 0	$ (7,838)	$ (7,838)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	51,957					51,957
Other comprehensive income, net of tax	11,048										11,048
Stock based compensation	1,822			1,822
Issuance of stock for Highlands acquisition	43,417			43,417
Retirement of restricted stock	(654)			(654)
Exercise of stock options	307			307
Cash dividends on common stock	(18,557)					(18,557)
Balance at end of period at Sep. 30, 2019	713,204			559,595		150,399			0		3,210
Balance at beginning of period at Jun. 30, 2019	698,463			558,768		137,887			0		1,808
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	18,874					18,874
Other comprehensive income, net of tax	1,402										1,402
Stock based compensation	558			558
Retirement of restricted stock	(38)			(38)
Exercise of stock options	307			307
Cash dividends on common stock	(6,362)					(6,362)
Balance at end of period at Sep. 30, 2019	713,204			559,595		150,399			0		3,210
Balance at beginning of period at Dec. 31, 2019	725,263			560,263		162,752			0		2,248
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	38,670					38,670
Other comprehensive income, net of tax	8,630										8,630
Purchase of treasury stock, 131,035 shares	(1,452)								(1,452)
Stock based compensation	2,046			2,046
Retirement of restricted stock	(492)			(492)
Cash dividends on common stock	(19,093)					(19,093)
Balance at end of period at Sep. 30, 2020	753,572			561,817		182,329			(1,452)		10,878
Balance at beginning of period at Jun. 30, 2020	745,489			561,257		174,267			(1,452)		11,417
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	14,427					14,427
Other comprehensive income, net of tax	(539)										(539)
Stock based compensation	585			585
Retirement of restricted stock	(25)			(25)
Cash dividends on common stock	(6,365)					(6,365)
Balance at end of period at Sep. 30, 2020	$ 753,572			$ 561,817		$ 182,329			$ (1,452)		$ 10,878