Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2018	$ 2,247,573	$ 554,377	$ 1,489,703	$ 946,032	$ (59,063)	$ (683,476)
Beginning Balance (in shares) at Dec. 31, 2018		170,184
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	56,663			56,663
Other comprehensive income	21,430				21,430
Stock issued (in shares)		115
Stock issued	1,657	$ 108	607			942
Stock-based compensation awards (in shares)
Stock-based compensation awards	1,560		1,560
Acquisition of treasury stock (in shares)		(376)
Acquisition of treasury stock (in shares)	(5,877)					(5,877)
Common stock cash dividends	(21,987)			(21,987)
Ending Balance at Mar. 31, 2019	2,301,019	$ 554,485	1,491,870	980,708	(37,633)	(688,411)
Ending Balance (in shares) at Mar. 31, 2019		169,923
Beginning Balance at Dec. 31, 2019	2,342,176	$ 556,110	1,499,681	1,079,391	(137)	(792,869)
Beginning Balance (in shares) at Dec. 31, 2019		164,218
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	26,047
Other comprehensive income	18,445				18,445
Stock issued (in shares)		125
Stock issued	2,001	$ 133	889			979
Stock-based compensation awards (in shares)
Stock-based compensation awards	1,619		1,619
Acquisition of treasury stock (in shares)		(2,908)
Acquisition of treasury stock (in shares)	(39,748)					(39,748)
Common stock cash dividends	(20,985)			(20,985)
Ending Balance at Mar. 31, 2020	$ 2,285,748	$ 556,243	$ 1,502,189	$ 1,040,646	$ 18,308	$ (831,638)
Ending Balance (in shares) at Mar. 31, 2020		161,435