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, 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	79,873				79,873
Other comprehensive income (loss), net of tax	36,024					36,024
Cash dividends on common stock	(23,847)				(23,847)
Share-based compensation (in shares)			108,638
Share-based compensation	1,825		$ 14	1,811
Stock issued under employee benefit plans (in shares)			11,247
Stock issued under employee benefit plans	362		$ 1	361
Stock issued under dividend reinvestment and stock purchase plan (in shares)			18,686
Stock issued under dividend reinvestment and stock purchase plan	709		$ 2	707
Stock options exercised (in shares)			11,200
Stock options exercised	105		$ 1	104
Stock redeemed (in shares)			(42,977)
Restricted shares withheld for taxes	(1,675)		$ (5)	(1,670)
Ending balance (in shares) at Jun. 30, 2019		125	49,456,594
Ending balance at Jun. 30, 2019	1,501,636	$ 125	$ 6,182	841,365	639,362	14,602
Beginning balance (in shares) at Mar. 31, 2019		125	49,428,468
Beginning balance at Mar. 31, 2019	1,455,848	$ 125	$ 6,179	839,919	611,220	(1,595)
Comprehensive income:
Net income	41,056				41,056
Other comprehensive income (loss), net of tax	16,197					16,197
Cash dividends on common stock	(12,914)				(12,914)
Share-based compensation (in shares)			4,978
Share-based compensation	844		$ 1	843
Stock issued under employee benefit plans (in shares)			5,908
Stock issued under employee benefit plans	188			188
Stock issued under dividend reinvestment and stock purchase plan (in shares)			10,178
Stock issued under dividend reinvestment and stock purchase plan	369		$ 1	368
Stock options exercised (in shares)			7,500
Stock options exercised	65		$ 1	64
Stock redeemed (in shares)			(438)
Restricted shares withheld for taxes	(17)			(17)
Ending balance (in shares) at Jun. 30, 2019		125	49,456,594
Ending balance at Jun. 30, 2019	1,501,636	$ 125	$ 6,182	841,365	639,362	14,602
Beginning balance (in shares) at Dec. 31, 2019		125	55,368,482
Beginning balance at Dec. 31, 2019	1,786,437	$ 125	$ 6,921	1,054,997	696,520	27,874
Comprehensive income:
Net income	67,255				67,255
Other comprehensive income (loss), net of tax	35,971					35,971
Cash dividends on common stock	(28,336)				(28,336)
Repurchase of common stock (in shares)			(1,634,437)
Repurchases of common stock	(55,912)		$ (204)	(55,708)
Share-based compensation (in shares)			8,591
Share-based compensation	2,433		$ 1	2,432
Stock issued under employee benefit plans (in shares)			11,511
Stock issued under employee benefit plans	309		$ 1	308
Stock issued under dividend reinvestment and stock purchase plan (in shares)			31,607
Stock issued under dividend reinvestment and stock purchase plan	$ 863		$ 4	859
Stock options exercised (in shares)	10,050		10,050
Stock options exercised	$ 83		$ 1	82
Stock redeemed (in shares)			(304)
Restricted shares withheld for taxes	(8)			(8)
Ending balance (in shares) at Jun. 30, 2020		125	53,795,500
Ending balance at Jun. 30, 2020	1,809,095	$ 125	$ 6,724	1,002,962	735,439	63,845
Beginning balance (in shares) at Mar. 31, 2020		125	53,754,137
Beginning balance at Mar. 31, 2020	1,777,960	$ 125	$ 6,719	1,000,942	716,518	53,656
Comprehensive income:
Net income	32,992				32,992
Other comprehensive income (loss), net of tax	10,189					10,189
Cash dividends on common stock	(14,071)				(14,071)
Share-based compensation (in shares)			5,259
Share-based compensation	1,213		$ 1	1,212
Stock issued under employee benefit plans (in shares)			11,511
Stock issued under employee benefit plans	309		$ 1	308
Stock issued under dividend reinvestment and stock purchase plan (in shares)			15,897
Stock issued under dividend reinvestment and stock purchase plan	435		$ 2	433
Stock options exercised (in shares)			9,000
Stock options exercised	76		$ 1	75
Stock redeemed (in shares)			(304)
Restricted shares withheld for taxes	(8)			(8)
Ending balance (in shares) at Jun. 30, 2020		125	53,795,500
Ending balance at Jun. 30, 2020	$ 1,809,095	$ 125	$ 6,724	$ 1,002,962	$ 735,439	$ 63,845