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, 2018	$ 1,264,753	$ 805	$ 107,455	$ 1,413,746	$ (16,073)	$ (241,180)
Comprehensive income	36,599	0	0	36,086	513	0
Purchases of common stock	(20,545)	0	0	0	0	(20,545)
Dividends on common stock	(6,290)	0	0	(6,290)	0	0
Equity compensation activity	(1,179)	0	(1,578)	0	0	399
Non-cash equity compensation expense	2,051	0	2,051	0	0	0
BALANCE at Mar. 31, 2019	1,275,389	805	107,928	1,443,542	(15,560)	(261,326)
BALANCE at Dec. 31, 2018	1,264,753	805	107,455	1,413,746	(16,073)	(241,180)
Comprehensive income	80,337
BALANCE at Jun. 30, 2019	1,032,344	805	110,102	1,219,529	(15,140)	(282,952)
BALANCE at Mar. 31, 2019	1,275,389	805	107,928	1,443,542	(15,560)	(261,326)
Comprehensive income	43,738	0	0	43,318	420	0
Purchases of common stock	(21,756)	0	0	0	0	(21,756)
Dividends on common stock	(267,331)	0	0	(267,331)	0	0
Equity compensation activity	(10)	0	(140)	0	0	130
Non-cash equity compensation expense	2,314	0	2,314	0	0	0
BALANCE at Jun. 30, 2019	1,032,344	805	110,102	1,219,529	(15,140)	(282,952)
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, 2019	1,111,008	805	112,649	1,294,608	(14,728)	(282,326)
Comprehensive income	47,006
BALANCE at Jun. 30, 2020	1,136,388	805	111,634	1,344,361	(29,912)	(290,500)
BALANCE at Mar. 31, 2020	1,102,036	805	110,695	1,311,448	(30,218)	(290,694)
Comprehensive income	39,438	0	0	39,132	306	0
Dividends on common stock	(6,219)	0	0	(6,219)	0	0
Equity compensation activity	(5)	0	(199)	0	0	194
Non-cash equity compensation expense	1,138	0	1,138	0	0	0
BALANCE at Jun. 30, 2020	$ 1,136,388	$ 805	$ 111,634	$ 1,344,361	$ (29,912)	$ (290,500)