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	$ 556,778	$ 141,096	$ 225,037
OTHER COMPREHENSIVE INCOME/(LOSS):
Foreign currency translation adjustment	106,861	(47,349)	(86,968)
Net unrealized gain/(loss) on qualifying cash flow hedges, net of tax (provision)/benefit	1,870	(5,666)	(3,837)
Changes in pension and other postretirement benefit obligations, net of tax benefit/(provision)	347	(30,953)	9,600
Other comprehensive income/(loss)	109,078	(83,968)	(81,205)
COMPREHENSIVE INCOME	665,856	57,128	143,832
Less: Comprehensive income attributable to noncontrolling interest	25,023	8,508	0
COMPREHENSIVE INCOME ATTRIBUTABLE TO G&W	$ 640,833	$ 48,620	$ 143,832