Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
BALANCE at Dec. 31, 2019	$ 1,111,008	$ 805	$ 112,649	$ 1,294,608	$ (14,728)	$ (282,326)
Comprehensive income	7,568	0	0	23,058	(15,490)	0
Purchases of common stock	(8,798)	0	0	0	0	(8,798)
Dividends on common stock	(6,218)	0	0	(6,218)	0	0
Equity compensation activity	(3,930)	0	(4,360)	0	0	430
Non-cash equity compensation expense	2,406	0	2,406	0	0	0
BALANCE at Mar. 31, 2020	1,102,036	805	110,695	1,311,448	(30,218)	(290,694)
BALANCE at Dec. 31, 2020	1,195,040	805	116,039	1,438,916	(22,833)	(337,887)
Comprehensive income	46,227	0	0	46,492	(265)	0
Purchases of common stock	(5,507)	0	0	0	0	(5,507)
Dividends on common stock	(6,792)	0	0	(6,792)	0	0
Equity compensation activity	(3,740)	0	(3,953)	0	0	213
Non-cash equity compensation expense	2,502	0	2,502	0	0	0
BALANCE at Mar. 31, 2021	$ 1,227,730	$ 805	$ 114,588	$ 1,478,616	$ (23,098)	$ (343,181)