Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulated adjustment for adoption of ASU	Common  Stock	Retained Earnings	Retained Earnings Cumulated adjustment for adoption of ASU	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulated adjustment for adoption of ASU
Balance at beginning of period at Dec. 31, 2017	$ 583,122		$ 512,734	$ 72,737	$ 2,043	$ 0	$ (2,349)	$ (2,043)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	63,401			63,401
Other comprehensive income (loss), net of tax	(3,446)						(3,446)
Stock based compensation	2,425		2,425
Retirement of restricted stock	(763)		(763)
Exercise of stock options	307		307
Cash dividends on common stock	(21,307)			(21,307)
Balance at end of period at Dec. 31, 2018	$ 623,739	$ 125	514,703	116,874	125	0	(7,838)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member
Net income	$ 70,672			70,672
Other comprehensive income (loss), net of tax	10,086						10,086
Issuance of stock for Highlands acquisition	43,417		43,417
Stock based compensation	2,545		2,545
Retirement of restricted stock	(715)		(715)
Exercise of stock options	313		313
Cash dividends on common stock	(24,919)			(24,919)
Balance at end of period at Dec. 31, 2019	$ 725,263	$ (3,395)	560,263	162,752	$ (3,395)	0	2,248
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Net income	$ 57,518			57,518
Other comprehensive income (loss), net of tax	9,149						9,149
Treasury stock	(1,452)					(1,452)
Stock based compensation	2,659		2,659
Retirement of restricted stock	(501)		(501)
Cash dividends on common stock	(25,457)			(25,457)
Balance at end of period at Dec. 31, 2020	$ 763,784		$ 562,421	$ 191,418		$ (1,452)	$ 11,397