Condensed Consolidated Statement Of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning balance at Dec. 31, 2018	$ 706,255	$ 280	$ 203,246	$ 563,496	$ (2,605)	$ (58,162)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	34,366			34,366
Issuance of shares of common stock pursuant to stock-based awards, net of shares tendered for payment of taxes	(6,348)	1	(6,349)
Stock-based compensation expense	3,733		3,733
Other comprehensive income (loss)					(1,328)
Cash dividends	(14,999)			(14,999)
Dividend equivalents on stock-based awards	0		304	(304)
Ending balance at Mar. 31, 2019	721,679	281	200,934	582,559	(3,933)	(58,162)
Beginning balance at Dec. 31, 2018	706,255	280	203,246	563,496	(2,605)	(58,162)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	81,893
Ending balance at Jun. 30, 2019	752,876	281	204,572	613,501	(7,316)	(58,162)
Beginning balance at Mar. 31, 2019	721,679	281	200,934	582,559	(3,933)	(58,162)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	47,527			47,527
Issuance of shares of common stock pursuant to stock-based awards, net of shares tendered for payment of taxes	(795)		(795)
Stock-based compensation expense	4,115		4,115
Other comprehensive income (loss)	(3,383)				(3,383)
Cash dividends	(16,267)			(16,267)
Dividend equivalents on stock-based awards	0		318	(318)
Ending balance at Jun. 30, 2019	752,876	281	204,572	613,501	(7,316)	(58,162)
Beginning balance at Dec. 31, 2019	800,672	281	212,485	644,945	1,123	(58,162)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	28,214			28,214
Issuance of shares of common stock pursuant to stock-based awards, net of shares tendered for payment of taxes	(4,517)	1	(4,518)
Stock-based compensation expense	3,295		3,295
Other comprehensive income (loss)	(3,540)				(3,540)
Cash dividends	(16,321)			(16,321)
Dividend equivalents on stock-based awards	0		297	(297)
Ending balance at Mar. 31, 2020	807,803	282	211,559	656,541	(2,417)	(58,162)
Beginning balance at Dec. 31, 2019	800,672	281	212,485	644,945	1,123	(58,162)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	41,400
Ending balance at Jun. 30, 2020	816,630	282	215,864	653,083	5,563	(58,162)
Beginning balance at Mar. 31, 2020	807,803	282	211,559	656,541	(2,417)	(58,162)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	13,186			13,186
Issuance of shares of common stock pursuant to stock-based awards, net of shares tendered for payment of taxes	(99)		(99)
Stock-based compensation expense	4,109		4,109
Other comprehensive income (loss)	7,980				7,980
Cash dividends	(16,349)			(16,349)
Dividend equivalents on stock-based awards	0		295	(295)
Ending balance at Jun. 30, 2020	$ 816,630	$ 282	$ 215,864	$ 653,083	$ 5,563	$ (58,162)