CONSOLIDATED CONDENSED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - 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, 2017		125	49,158,238
Beginning balance at Dec. 31, 2017	$ 1,303,463	$ 125	$ 6,145	$ 834,870	$ 465,231	$ (2,908)
Comprehensive income:
Net income	117,426				117,426
Other comprehensive income (loss), net of tax	(31,875)					(31,875)
Cash dividends on common stock	(30,732)				(30,732)
Issuance of common stock related to acquisition	0
Reclassification adjustment under ASU 2018-02	0				626	(626)
Share-based compensation (in shares)			106,833
Share-based compensation	2,546		$ 13	2,533
Stock issued under employee benefit plans (in shares)			13,448
Stock issued under employee benefit plans	515		$ 2	513
Stock issued under dividend reinvestment and stock purchase plan (in shares)			18,761
Stock issued under dividend reinvestment and stock purchase plan	879		$ 2	877
Stock options exercised (in shares)			51,243
Stock options exercised	1,093		$ 6	1,087
Stock redeemed (in shares)			(43,981)
Stock redeemed	(1,889)		$ (5)	(1,884)
Ending balance (in shares) at Sep. 30, 2018		125	49,304,542
Ending balance at Sep. 30, 2018	1,361,426	$ 125	$ 6,163	837,996	552,551	(35,409)
Beginning balance (in shares) at Jun. 30, 2018		125	49,280,188
Beginning balance at Jun. 30, 2018	1,340,328	$ 125	$ 6,160	836,549	522,362	(24,868)
Comprehensive income:
Net income	41,113				41,113
Other comprehensive income (loss), net of tax	(10,541)					(10,541)
Cash dividends on common stock	(10,924)				(10,924)
Share-based compensation (in shares)			8,812
Share-based compensation	891		$ 1	890
Stock issued under employee benefit plans (in shares)			4,243
Stock issued under employee benefit plans	174		$ 2	172
Stock issued under dividend reinvestment and stock purchase plan (in shares)			6,650
Stock issued under dividend reinvestment and stock purchase plan	324			324
Stock options exercised (in shares)			6,311
Stock options exercised	140			140
Stock redeemed (in shares)			(1,662)
Stock redeemed	(79)			(79)
Ending balance (in shares) at Sep. 30, 2018		125	49,304,542
Ending balance at Sep. 30, 2018	1,361,426	$ 125	$ 6,163	837,996	552,551	(35,409)
Beginning balance (in shares) at Dec. 31, 2018		125	49,349,800
Beginning balance at Dec. 31, 2018	1,408,260	$ 125	$ 6,169	840,052	583,336	(21,422)
Comprehensive income:
Net income	116,630				116,630
Other comprehensive income (loss), net of tax	47,070					47,070
Cash dividends on common stock	(36,793)				(36,793)
Issuance of common stock related to acquisition (in shares)			6,383,806
Issuance of common stock related to acquisition	229,926		$ 798	229,128
Reclassification adjustment under ASU 2018-02						(626)
Repurchase of common stock (in shares)			(516,016)
Repurchase of common stock	(19,041)		$ (65)	(18,976)
Share-based compensation (in shares)			113,043
Share-based compensation	2,887		$ 14	2,873
Stock issued under employee benefit plans (in shares)			16,117
Stock issued under employee benefit plans	518		$ 2	516
Stock issued under dividend reinvestment and stock purchase plan (in shares)			28,949
Stock issued under dividend reinvestment and stock purchase plan	$ 1,109		$ 3	1,106
Stock options exercised (in shares)	12,950		12,950
Stock options exercised	$ 121		$ 2	119
Stock redeemed (in shares)			(42,977)
Stock redeemed	(1,675)		$ (5)	(1,670)
Ending balance (in shares) at Sep. 30, 2019		125	55,345,672
Ending balance at Sep. 30, 2019	1,749,012	$ 125	$ 6,918	1,053,148	663,173	25,648
Beginning balance (in shares) at Jun. 30, 2019		125	49,456,594
Beginning balance at Jun. 30, 2019	1,501,636	$ 125	$ 6,182	841,365	639,362	14,602
Comprehensive income:
Net income	36,757				36,757
Other comprehensive income (loss), net of tax	11,046					11,046
Cash dividends on common stock	(12,946)				(12,946)
Issuance of common stock related to acquisition (in shares)			6,383,806
Issuance of common stock related to acquisition	229,926		$ 798	229,128
Repurchase of common stock (in shares)			(516,016)
Repurchase of common stock	(19,041)		$ (65)	(18,976)
Share-based compensation (in shares)			4,405
Share-based compensation	1,062			1,062
Stock issued under employee benefit plans (in shares)			4,870
Stock issued under employee benefit plans	156		$ 1	155
Stock issued under dividend reinvestment and stock purchase plan (in shares)			10,263
Stock issued under dividend reinvestment and stock purchase plan	400		$ 1	399
Stock options exercised (in shares)			1,750
Stock options exercised	16		$ 1	15
Stock redeemed	0
Ending balance (in shares) at Sep. 30, 2019		125	55,345,672
Ending balance at Sep. 30, 2019	$ 1,749,012	$ 125	$ 6,918	$ 1,053,148	$ 663,173	$ 25,648