Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings		Accumulated Other Comprehensive (Loss) Income		Treasury Stock
Beginning Balance at Dec. 31, 2015	$ 2,041,894	$ 547,141	$ 1,450,690	$ 641,588		$ (22,017)		$ (575,508)
Beginning Balance (in shares) at Dec. 31, 2015		174,176
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	161,625			161,625
Other comprehensive loss	(16,432)					(16,432)
Stock issued, including related tax benefits	17,131	$ 2,566	10,356					4,209
Stock issued, including related tax benefits (in shares)		1,350
Stock-based compensation awards	6,556		6,556
Acquisition of treasury stock	(18,545)							(18,545)
Acquisition of treasury stock (in shares)		(1,486)
Common stock cash dividends	(71,114)			(71,114)
Ending Balance at Dec. 31, 2016	2,121,115	$ 549,707	1,467,602	732,099		(38,449)		(589,844)
Ending Balance (in shares) at Dec. 31, 2016		174,040
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	171,753			171,753
Other comprehensive loss	5,475					5,475
Stock issued, including related tax benefits	8,538	$ 2,525	5,578					435
Stock issued, including related tax benefits (in shares)		1,130
Stock-based compensation awards	5,209		5,209
Common stock cash dividends	(82,233)			(82,233)
Ending Balance at Dec. 31, 2017	2,229,857	$ 552,232	1,478,389	821,619		(32,974)		(589,409)
Ending Balance (in shares) at Dec. 31, 2017		175,170
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	208,393			208,393
Other comprehensive loss	(18,988)					(18,988)
Stock issued, including related tax benefits	6,735	$ 2,062	3,432					1,241
Stock issued, including related tax benefits (in shares)		977
Stock-based compensation awards (in shares)		33
Stock-based compensation awards	7,965	$ 83	7,882
Acquisition of treasury stock	(95,308)							(95,308)
Reclassification of stranded tax effects	(7,101)			7,101	[1]	(7,101)	[1]
Acquisition of treasury stock (in shares)		(5,996)
Common stock cash dividends	(91,081)			(91,081)
Ending Balance at Dec. 31, 2018	$ 2,247,573	$ 554,377	$ 1,489,703	$ 946,032		$ (59,063)		$ (683,476)
Ending Balance (in shares) at Dec. 31, 2018		170,184

[1] Result of adoption of ASU 2018-02. See Note 1 to Consolidated Financial Statements for further details.