CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock and Additional Paid-In Capital	Retained Earnings	Cumulative Translation Adjustment	Retirement Benefits Adjustment	Cumulative Unrealized Gain (Loss) on Derivatives	Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustment for adoption of ASU | Accounting Standards Update 2016-16	$ (645)		$ (645)
Adjustment for adoption of ASU | Accounting Standards Update 2018-02	0		6,435		$ (3,411)	$ (3,024)
Balance, December 31, 2017 at Dec. 31, 2017	1,886,542	$ 717,808	2,057,915	$ (46,306)	(29,154)	(14,047)	$ (799,674)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	98,958		98,958
Cumulative translation adjustment	27,578			27,578
Net change in retirement obligations (net of tax of $505)	1,413				1,413
Net change on derivatives designated as cash flow hedges (net of tax of $371)	1,261					1,261
Issuance of 227,932 shares of common stock from issuance of unvested shares, performance share units and exercise of stock options (net of tax of $2,934)	6,590						6,590
Shares surrendered for tax withholding	(10,750)						(10,750)
Share-based compensation	5,938	5,938
Balance, March 31, 2018 at Mar. 31, 2018	$ 2,016,885	$ 723,746	$ 2,162,663	$ (18,728)	$ (31,152)	$ (15,810)	$ (803,834)