Consolidated Statement of Shareholders' Equity - USD ($)	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning Balance (in shares) at Dec. 31, 2017		29,141,467
Beginning Balance at Dec. 31, 2017	$ 635,656,000	$ 29,141,000	$ 185,332,000	$ 587,877,000	$ (115,814,000)	$ (50,880,000)
Beginning Balance (in shares) at Dec. 31, 2017						1,325,975
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) earnings	54,169,000	0	0	54,169,000	0	$ 0
Income Tax Effects Allocated Directly to Equity, Cumulative Effect of Change in Accounting Principle	(9,584,000)	0	0	(9,584,000)	0	0
Other comprehensive loss	$ (19,084,000)	0	0	0	(19,084,000)	0
Common Stock, Dividends, Per Share, Declared
Dividends (per share of common stock, $0.80 )	$ (22,359,000)	$ 0	0	(22,359,000)	0	0
Changes due to convertible notes transactions (in shares)		114,778
Stock Issued During Period, Value, Conversion of Convertible Securities		$ 115,000		$ 0	$ 0	$ 0
Adjustments to Equity, Equity Component of Convertible Debt	(8,000)
Adjustments to Additional Paid in Capital, Convertible Debt with Conversion Feature			$ (123,000)
Purchase of treasury shares (in shares)		0	0	0	0	313,330
Purchase of treasury shares	(19,489,000)	$ 0				$ (19,489,000)
Employee stock plans (in shares)		226,722
Employee stock plans	7,351,000	$ 227,000	$ 8,813,000	$ 0	$ 0
Employee stock plans (in shares)						25,069
Employee stock plans						$ (1,689,000)
Share-based compensation expense (in shares)		61,747
Share-based compensation expense	6,505,000	$ 62,000	6,452,000	0	0
Share-based compensation expense (in shares)						8,543
Share-based compensation expense						$ (9,000)
Ending Balance (in shares) at Dec. 31, 2018		29,544,714
Ending Balance at Dec. 31, 2018	633,157,000	$ 29,545,000	200,474,000	610,103,000	(134,898,000)	$ (72,067,000)
Ending Balance (in shares) at Dec. 31, 2018						1,672,917
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) earnings	209,829,000	0	0	209,829,000	0	$ 0
Income Tax Effects Allocated Directly to Equity, Cumulative Effect of Change in Accounting Principle	0	0	0	(23,094,000)	(23,094,000)	0
Other comprehensive loss	$ 7,099,000	0	0	0	7,099,000	0
Common Stock, Dividends, Per Share, Declared
Dividends (per share of common stock, $0.80 )	$ (22,360,000)	$ 0	0	(22,360,000)	0	$ 0
Changes due to convertible notes transactions (in shares)		0				0
Stock Issued During Period, Value, Conversion of Convertible Securities		$ 0		0	0	$ 0
Adjustments to Equity, Equity Component of Convertible Debt	(18,000)
Adjustments to Additional Paid in Capital, Convertible Debt with Conversion Feature			(18,000)
Purchase of treasury shares (in shares)		0				522,622
Purchase of treasury shares	(31,785,000)	$ 0	0	0	0	$ (31,785,000)
Employee stock plans (in shares)		449,937
Employee stock plans	19,676,000	$ 449,000	20,151,000	0	0
Employee stock plans (in shares)						(17,609)
Employee stock plans						$ (924,000)
Share-based compensation expense (in shares)		63,804
Share-based compensation expense	7,604,000	$ 64,000	7,546,000	0	0
Share-based compensation expense (in shares)						6,184
Share-based compensation expense						$ (6,000)
Ending Balance (in shares) at Dec. 31, 2019		30,058,455
Ending Balance at Dec. 31, 2019	$ 823,202,000	$ 30,058,000	228,153,000	820,666,000	(150,893,000)	$ (104,782,000)
Ending Balance (in shares) at Dec. 31, 2019	2,219,332					2,219,332
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) earnings	$ (69,742,000)	0	0		0	$ 0
Other comprehensive loss	$ 20,072,000	0	0	0	20,072,000	0
Common Stock, Dividends, Per Share, Declared
Dividends (per share of common stock, $0.80 )	$ (22,160,000)	$ 0	0	(22,160,000)	0	$ 0
Purchase of treasury shares (in shares)		0				302,778
Purchase of treasury shares	(14,209,000)	$ 0	0	0	0	$ (14,209,000)
Employee stock plans (in shares)		164,149
Employee stock plans	4,296,000	$ 164,000	5,752,000	0	0
Employee stock plans (in shares)						32,150
Employee stock plans						$ (1,620,000)
Share-based compensation expense (in shares)		56,064
Share-based compensation expense	4,979,000	$ 57,000	4,924,000	0	0
Share-based compensation expense (in shares)						1,525
Share-based compensation expense						$ (2,000)
Ending Balance (in shares) at Dec. 31, 2020		30,278,668
Ending Balance at Dec. 31, 2020	$ 746,438,000	$ 30,279,000	$ 238,829,000	$ 728,764,000	$ (130,821,000)	$ (120,613,000)
Ending Balance (in shares) at Dec. 31, 2020	2,555,785					2,555,785