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
Balance 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
Adjustment for adoption of ASU			6,435		(3,411)	(3,024)
Adjustment for adoption of ASU | Accounting Standards Update 2016-16	(645)		(645)
Cumulative translation adjustment	27,578			27,578
Net change in retirement obligations (net of tax)	1,413				1,413
Net change on derivatives designated as cash flow hedges (net of tax)	1,261					1,261
Issuance of shares of common stock from issuance of unvested shares, performance share units and exercise of stock options (net of tax)	6,590						6,590
Shares surrendered for tax withholding	(10,750)						(10,750)
Share-based compensation	5,938	5,938
Balance at Mar. 31, 2018	2,016,885	723,746	2,162,663	(18,728)	(31,152)	(15,810)	(803,834)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustment for adoption of ASU | Accounting Standards Update 2016-02	28		28
Balance at Dec. 31, 2018	1,994,640	739,240	2,342,079	(94,420)	(22,740)	(12,065)	(957,454)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	110,268		110,268
Cumulative translation adjustment	(3,281)			(3,281)
Net change in retirement obligations (net of tax)	1,262				1,262
Net change on derivatives designated as cash flow hedges (net of tax)	1,227					1,227
Issuance of shares of common stock from issuance of unvested shares, performance share units and exercise of stock options (net of tax)	8,870						8,870
Repurchase of 369,810 shares of common stock	(51,706)						(51,706)
Shares surrendered for tax withholding	(11,479)						(11,479)
Share-based compensation	5,403	5,403
Balance at Mar. 31, 2019	$ 2,055,232	$ 744,643	$ 2,452,375	$ (97,701)	$ (21,478)	$ (10,838)	$ (1,011,769)