Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	COMMON STOCK [Member]	CAPITAL SURPLUS [Member]	RETAINED EARNINGS [Member]	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) [Member]
Balance at beginning of period at Dec. 31, 2021		$ 32,603	$ 159,914	$ 977,067	$ 2,150
Shares issued for stock options		253	6,758
Net income	$ 135,974			135,974
Dividends on common stock				(36,725)
Stock-based compensation arrangements			1,545
Net change					(84,390)
Balance at end of period at Sep. 30, 2022	1,195,149	32,856	168,217	1,076,316	(82,240)
Balance at beginning of period at Jun. 30, 2022		32,781	165,295	1,034,107	(46,488)
Shares issued for stock options		75	2,295
Net income	55,352			55,352
Dividends on common stock				(13,143)
Stock-based compensation arrangements			627
Net change					(35,752)
Balance at end of period at Sep. 30, 2022	1,195,149	32,856	168,217	1,076,316	(82,240)
Balance at beginning of period at Dec. 31, 2022	1,250,836	32,876	169,231	1,120,292	(71,563)
Shares issued for stock options		66	2,000
Net income	163,531			163,531
Dividends on common stock				(40,492)
Shares acquired and canceled		(21)		(1,799)
Stock-based compensation arrangements			2,077
Net change					(5,614)
Balance at end of period at Sep. 30, 2023	1,370,584	32,921	173,308	1,241,532	(77,177)
Balance at beginning of period at Jun. 30, 2023		32,939	172,358	1,206,499	(71,005)
Shares issued for stock options		3	86
Net income	50,988			50,988
Dividends on common stock				(14,156)
Shares acquired and canceled		(21)		(1,799)
Stock-based compensation arrangements			864
Net change					(6,172)
Balance at end of period at Sep. 30, 2023	$ 1,370,584	$ 32,921	$ 173,308	$ 1,241,532	$ (77,177)