Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 521,759	$ 692,164	$ 752,207
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	46,280	(9,288)	(55,362)
Derivative financial instruments	(29,778)	6,638	(13,156)
Marketable securities	1,194	(100)	(394)
Pension and postretirement benefit plans	47,636	52,574	(31,350)
Total other comprehensive income (loss), net of tax	65,332	49,824	(100,262)
Comprehensive income	$ 587,091	$ 741,988	$ 651,945