Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2017		49,321,231
Beginning balance at Dec. 31, 2017	$ 1,514,983	$ 249,951	$ (19,906)	$ 898,095	$ 397,354	$ (10,511)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	33,826				33,826
Other comprehensive income (loss)	(6,985)					(6,985)
Comprehensive income	26,841
Cash dividends	(9,455)				(9,455)
Issuance of common stock for stock-based compensation awards (in shares)		71,747
Issuance of common stock for stock-based compensation awards	(1,482)		1,610	(3,092)
Stock-based compensation expense	1,858			1,858
Other, net	20			20
Ending balance (in shares) at Mar. 31, 2018		49,392,978.000
Ending balance at Mar. 31, 2018	1,532,765	$ 249,951	(18,296)	896,881	421,725	(17,496)
Beginning balance (in shares) at Dec. 31, 2018		58,546,480
Beginning balance at Dec. 31, 2018	2,043,913	$ 296,483	(24,245)	1,288,911	500,660	(17,896)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	45,110				45,110
Other comprehensive income (loss)	10,446					10,446
Comprehensive income	55,556
Cash dividends	(12,442)				(12,442)
Issuance of common stock for stock-based compensation awards (in shares)		87,150
Issuance of common stock for stock-based compensation awards	(787)		2,655	(3,442)
Stock-based compensation expense	2,637			2,637
Ending balance (in shares) at Mar. 31, 2019		58,633,630.00
Ending balance at Mar. 31, 2019	$ 2,088,877	$ 296,483	$ (21,590)	$ 1,288,106	$ 533,328	$ (7,450)