CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Preferred	Common Stock	Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2016		125	40,912,697
Beginning balance at Dec. 31, 2016	$ 901,657	$ 125	$ 5,114	$ 509,018	$ 400,981	$ (13,581)
Comprehensive income
Net income	96,070				96,070
Other comprehensive income (loss), net of tax	10,673					10,673
Cash dividends on common stock	(31,820)				(31,820)
Issuance of common stock related to acquisitions (in shares)			8,044,446
Issuance of common stock related to acquisitions	321,431		$ 1,006	320,425
Share-based compensation (in shares)			89,362
Share-based compensation	2,827		$ 11	2,816
Stock issued under employee benefit plans (in shares)			14,948
Stock issued under employee benefit plans	519		$ 2	517
Stock issued under dividend reinvestment and stock purchase plan (in shares)			24,058
Stock issued under dividend reinvestment and stock purchase plan	991		$ 3	988
Stock options exercised (in shares)			104,748
Stock options exercised	2,398		$ 13	2,385
Stock redeemed (in shares)			(32,021)
Restricted shares withheld for taxes	(1,283)		$ (4)	(1,279)
Ending balance (in shares) at Dec. 31, 2017		125	49,158,238
Ending balance at Dec. 31, 2017	1,303,463	$ 125	$ 6,145	834,870	465,231	(2,908)
Comprehensive income
Net income	159,139				159,139
Other comprehensive income (loss), net of tax	(17,888)					(17,888)
Cash dividends on common stock	(41,660)				(41,660)
Reclassification adjustment under ASU 2018-02	(626)				626	(626)
Issuance of common stock related to acquisitions	0
Share-based compensation (in shares)			112,569
Share-based compensation	3,592		$ 14	3,578
Stock issued under employee benefit plans (in shares)			19,001
Stock issued under employee benefit plans	707		$ 2	705
Stock issued under dividend reinvestment and stock purchase plan (in shares)			28,156
Stock issued under dividend reinvestment and stock purchase plan	1,211		$ 4	1,207
Stock options exercised (in shares)			76,152
Stock options exercised	1,598		$ 10	1,588
Stock redeemed (in shares)			(44,316)
Restricted shares withheld for taxes	(1,902)		$ (6)	(1,896)
Ending balance (in shares) at Dec. 31, 2018		125	49,349,800
Ending balance at Dec. 31, 2018	1,408,260	$ 125	$ 6,169	840,052	583,336	(21,422)
Comprehensive income
Net income	164,460				164,460
Other comprehensive income (loss), net of tax	49,296					49,296
Cash dividends on common stock	(51,276)				(51,276)
Issuance of common stock related to acquisitions (in shares)			6,383,806
Issuance of common stock related to acquisitions	229,926		$ 798	229,128
Repurchases of common stock (in shares)			(516,016)
Repurchases of common stock	(19,041)		$ (65)	(18,976)
Share-based compensation (in shares)			116,572
Share-based compensation	4,115		$ 15	4,100
Stock issued under employee benefit plans (in shares)			21,521
Stock issued under employee benefit plans	702		$ 3	699
Stock issued under dividend reinvestment and stock purchase plan (in shares)			38,942
Stock issued under dividend reinvestment and stock purchase plan	$ 1,531		$ 5	1,526
Stock options exercised (in shares)	16,950		16,950
Stock options exercised	$ 144		$ 2	142
Stock redeemed (in shares)			(43,093)
Restricted shares withheld for taxes	(1,680)		$ (6)	(1,674)
Ending balance (in shares) at Dec. 31, 2019		125	55,368,482
Ending balance at Dec. 31, 2019	$ 1,786,437	$ 125	$ 6,921	$ 1,054,997	$ 696,520	$ 27,874