Condensed Consolidated Statements Of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Beginning Balance at Dec. 31, 2017		$ 1,751	$ 262,201	$ 1,809,845	$ (188,973)	$ (1,118,759)
Beginning Balance (in shares) at Dec. 31, 2017		110,385
Increase (Decrease) in Stockholders' Equity
Net income	$ 185,802			185,802
Other comprehensive (loss) income	$ (23,283)				(23,283)
Dividends declared on common stock				(33,833)
Dividends per share (usd per share)	$ 0.30
Stock compensation expense			11,162
Net issuance of treasury stock for vested restricted stock units (in shares)		233
Net issuance of treasury stock for vested restricted stock units			(1,062)			(1,995)
Adoption of accounting standards update related to leases in 2019 and revenue recognition in 2018				9,061
Ending Balance at Sep. 30, 2018	$ 911,917	$ 1,751	272,301	1,970,875	(212,256)	(1,120,754)
Ending Balance (in shares) at Sep. 30, 2018		110,618
Beginning Balance at Jun. 30, 2018		$ 1,751	268,559	1,897,417	(208,963)	(1,120,754)
Beginning Balance (in shares) at Jun. 30, 2018		110,618
Increase (Decrease) in Stockholders' Equity
Net income	84,739			84,739
Other comprehensive (loss) income	$ (3,293)				(3,293)
Dividends declared on common stock				(11,281)
Dividends per share (usd per share)	$ 0.10
Stock compensation expense			3,742
Net issuance of treasury stock for vested restricted stock units (in shares)		0
Net issuance of treasury stock for vested restricted stock units			0			0
Adoption of accounting standards update related to leases in 2019 and revenue recognition in 2018				0
Ending Balance at Sep. 30, 2018	$ 911,917	$ 1,751	272,301	1,970,875	(212,256)	(1,120,754)
Ending Balance (in shares) at Sep. 30, 2018		110,618
Beginning Balance at Dec. 31, 2018	881,265	$ 1,751	276,062	1,997,785	(268,808)	(1,125,525)
Beginning Balance (in shares) at Dec. 31, 2018		110,430
Increase (Decrease) in Stockholders' Equity
Net income	158,970			158,970
Other comprehensive (loss) income	$ (19,115)				(19,115)
Dividends declared on common stock				(37,302)
Dividends per share (usd per share)	$ 0.33
Stock compensation expense			12,669
Net issuance of treasury stock for vested restricted stock units (in shares)		746
Net issuance of treasury stock for vested restricted stock units			(3,670)			(11,582)
Adoption of accounting standards update related to leases in 2019 and revenue recognition in 2018				(593)
Repurchases of common stock						(12,112)
Repurchases of common stock, shares		(408)
Ending Balance at Sep. 30, 2019	$ 968,530	$ 1,751	285,061	2,118,860	(287,923)	(1,149,219)
Ending Balance (in shares) at Sep. 30, 2019		110,768
Beginning Balance at Jun. 30, 2019		$ 1,751	280,636	2,049,995	(265,373)	(1,137,107)
Beginning Balance (in shares) at Jun. 30, 2019		111,176
Increase (Decrease) in Stockholders' Equity
Net income	81,274			81,274
Other comprehensive (loss) income	$ (22,550)				(22,550)
Dividends declared on common stock				(12,409)
Dividends per share (usd per share)	$ 0.11
Stock compensation expense			4,425
Net issuance of treasury stock for vested restricted stock units (in shares)		0
Net issuance of treasury stock for vested restricted stock units			0			0
Adoption of accounting standards update related to leases in 2019 and revenue recognition in 2018				0
Repurchases of common stock						(12,112)
Repurchases of common stock, shares		(408)
Ending Balance at Sep. 30, 2019	$ 968,530	$ 1,751	$ 285,061	$ 2,118,860	$ (287,923)	$ (1,149,219)
Ending Balance (in shares) at Sep. 30, 2019		110,768