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, 2016	$ 994,787	$ 805	$ 101,035	$ 1,084,796	$ (16,917)	$ (174,932)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	203,971	0	0	202,889	1,082	0
Dividends on common stock	(19,523)	0	0	(19,523)	0	0
Equity compensation activity, including excess tax benefits	829	0	(3,481)	0	0	4,310
Non-cash equity compensation expense	4,546	0	4,546	0	0	0
Cumulative effect of accounting change	172	0	463	(291)	0	0
BALANCE at Dec. 31, 2017	1,184,782	805	102,563	1,267,871	(15,835)	(170,622)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	167,910	0	0	168,148	(238)	0
Purchases of common stock	(72,165)	0	0	0	0	(72,165)
Dividends on common stock	(24,284)	0	0	(24,284)	0	0
Equity compensation activity, including excess tax benefits	(895)	0	(2,502)	0	0	1,607
Non-cash equity compensation expense	7,394	0	7,394	0	0	0
Cumulative effect of accounting change	2,011	0	0	2,011	0	0
BALANCE at Dec. 31, 2018	1,264,753	805	107,455	1,413,746	(16,073)	(241,180)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	168,289	0	0	166,944	1,345	0
Purchases of common stock	(42,301)	0	0	0	0	(42,301)
Dividends on common stock	(286,082)	0	0	(286,082)	0	0
Equity compensation activity, including excess tax benefits	(1,728)	0	(2,883)	0	0	1,155
Non-cash equity compensation expense	8,077	0	8,077	0	0	0
BALANCE at Dec. 31, 2019	$ 1,111,008	$ 805	$ 112,649	$ 1,294,608	$ (14,728)	$ (282,326)