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, 2017	$ 1,184,782	$ 805	$ 102,563	$ 1,267,871	$ (15,835)	$ (170,622)
Comprehensive income	30,410	0	0	27,807	2,603	0
Dividends on common stock	(5,071)	0	0	(5,071)	0	0
Equity compensation activity	(438)	0	(1,069)	0	0	631
Non-cash equity compensation expense	1,410	0	1,410	0	0	0
Cumulative effect of accounting change	2,011	0	0	2,011	0	0
BALANCE at Mar. 31, 2018	1,213,104	805	102,904	1,292,618	(13,232)	(169,991)
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)