CONSOLIDATED STATEMENT OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Total
Balance at Dec. 31, 2019	$ 56,841	$ 370,867	$ 50,742	$ 6,047	$ 484,497
Balance, shares at Dec. 31, 2019	56,840,521
Net income			12,591		12,591
Common stock issued from option exercises, net of tax benefits	$ 74	546			620
Common stock issued from option exercises, net of tax benefits, shares	74,000
Common stock issued from restricted units, net of tax benefits	$ 411	(411)
Common stock issued from restricted units, net of tax benefits, shares	411,035
Stock-based compensation		1,216			1,216
Other comprehensive income (loss) net of reclassification adjustments and tax				1,553	1,553
Balance (Accounting Standards Update 2016-13 [Member]) at Mar. 31, 2020			(2,373)		(2,373)
Balance at Mar. 31, 2020	$ 57,326	372,218	60,960	7,600	498,104
Balance (in shares) at Mar. 31, 2020	57,325,556
Balance at Dec. 31, 2019	$ 56,841	370,867	50,742	6,047	484,497
Balance, shares at Dec. 31, 2019	56,840,521
Net income					55,913
Other comprehensive income (loss) net of reclassification adjustments and tax					14,654
Balance at Sep. 30, 2020	$ 57,491	375,985	104,282	20,701	558,459
Balance (in shares) at Sep. 30, 2020	57,490,874
Balance at Mar. 31, 2020	$ 57,326	372,218	60,960	7,600	498,104
Balance, shares at Mar. 31, 2020	57,325,556
Net income			20,068		20,068
Common stock issued from restricted units, net of tax benefits	$ 129	(129)
Common stock issued from restricted units, net of tax benefits, shares	129,752
Stock-based compensation		1,723			1,723
Other comprehensive income (loss) net of reclassification adjustments and tax				13,184	13,184
Balance at Jun. 30, 2020	$ 57,455	373,812	81,028	20,784	533,079
Balance (in shares) at Jun. 30, 2020	57,455,308
Net income			23,254		23,254
Common stock issued from restricted units, net of tax benefits	$ 36	(36)
Common stock issued from restricted units, net of tax benefits, shares	35,566
Stock-based compensation		2,209			2,209
Other comprehensive income (loss) net of reclassification adjustments and tax				(83)	(83)
Balance at Sep. 30, 2020	$ 57,491	375,985	104,282	20,701	558,459
Balance (in shares) at Sep. 30, 2020	57,490,874
Balance at Dec. 31, 2020	$ 57,551	377,452	128,453	17,708	$ 581,164
Balance, shares at Dec. 31, 2020	57,550,629				57,550,629
Net income			25,965		$ 25,965
Common stock issued from option exercises, net of tax benefits	$ 61	404			465
Common stock issued from option exercises, net of tax benefits, shares	61,500
Common stock issued from restricted units, net of tax benefits	$ 230	(230)
Common stock issued from restricted units, net of tax benefits, shares	230,212
Stock-based compensation		2,261			2,261
Common stock repurchases	$ (594)	(9,406)			(10,000)
Common stock repurchases, shares	(594,428)
Other comprehensive income (loss) net of reclassification adjustments and tax				(3,091)	(3,091)
Balance at Mar. 31, 2021	$ 57,248	370,481	154,418	14,617	596,764
Balance (in shares) at Mar. 31, 2021	57,247,913
Balance at Dec. 31, 2020	$ 57,551	377,452	128,453	17,708	$ 581,164
Balance, shares at Dec. 31, 2020	57,550,629				57,550,629
Net income					$ 83,661
Common stock repurchases, shares					(1,484,630)
Other comprehensive income (loss) net of reclassification adjustments and tax					$ (6,704)
Balance at Sep. 30, 2021	$ 57,331	357,528	212,114	11,004	$ 637,977
Balance (in shares) at Sep. 30, 2021	57,330,846				57,330,846
Balance at Mar. 31, 2021	$ 57,248	370,481	154,418	14,617	$ 596,764
Balance, shares at Mar. 31, 2021	57,247,913
Net income			29,435		29,435
Common stock issued from option exercises, net of tax benefits	$ 217	547			764
Common stock issued from option exercises, net of tax benefits, shares	217,368
Common stock issued from restricted units, net of tax benefits	$ 442	(442)
Common stock issued from restricted units, net of tax benefits, shares	442,321
Stock-based compensation		2,206			2,206
Common stock repurchases	$ (449)	(9,551)			(10,000)
Common stock repurchases, shares	(449,315)
Other comprehensive income (loss) net of reclassification adjustments and tax				(60)	(60)
Balance at Jun. 30, 2021	$ 57,458	363,241	183,853	14,557	619,109
Balance (in shares) at Jun. 30, 2021	57,458,287
Net income			28,261		28,261
Common stock issued from option exercises, net of tax benefits	$ 314	1,790			2,104
Common stock issued from option exercises, net of tax benefits, shares	313,446
Stock-based compensation		2,056			2,056
Common stock repurchases	$ (441)	(9,559)			$ (10,000)
Common stock repurchases, shares	(440,887)				(440,887)
Other comprehensive income (loss) net of reclassification adjustments and tax				(3,553)	$ (3,553)
Balance at Sep. 30, 2021	$ 57,331	$ 357,528	$ 212,114	$ 11,004	$ 637,977
Balance (in shares) at Sep. 30, 2021	57,330,846				57,330,846