CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - 6 months ended Jun. 30, 2016 - 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, 2015	$ 1,443,291	$ 680,525	$ 1,666,680	$ (92,979)	$ (30,901)	$ (22,618)	$ (757,416)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	143,889		143,889
Cumulative translation adjustment	(10,826)			(10,826)
Net change in retirement obligations (net of tax of $643)	1,262				1,262
Net change on derivatives designated as cash flow hedges (net of tax of $1,253)	2,190					2,190
Issuance of 311,017 shares of common stock from issuance of unvested shares, performance share units and exercise of stock options	16,934						16,934
Repurchase of 725,993 shares of common stock	(53,890)						(53,890)
Unvested shares surrendered for tax withholding	(4,830)						(4,830)
Share-based compensation	10,322	10,322
Cash dividends declared - $0.68 per common share outstanding	(51,412)		(51,412)
Balance at Jun. 30, 2016	$ 1,496,930	$ 690,847	$ 1,759,157	$ (103,805)	$ (29,639)	$ (20,428)	$ (799,202)