Accumulated Other Comprehensive Income/(Loss) AOCI Attributbale to G&W (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, beginning balance	$ (211,336)	$ (153,457)
Other comprehensive income/(loss) before reclassifications	72,147	3,574
Amounts reclassified from accumulated other comprehensive loss, net of tax (provision)/benefit	8,050	(13,948)
Current period change in OCI	80,197	(10,374)
Accumulated other comprehensive income loss, ending balance	(131,139)	(163,831)
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, beginning balance	(177,662)	(156,146)
Other comprehensive income/(loss) before reclassifications	81,412	3,618
Amounts reclassified from accumulated other comprehensive loss, net of tax (provision)/benefit	0	0
Current period change in OCI	81,412	3,618
Accumulated other comprehensive income loss, ending balance	(96,250)	(152,528)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, beginning balance	(19,948)	11,005
Other comprehensive income/(loss) before reclassifications	(2,262)	4,305
Amounts reclassified from accumulated other comprehensive loss, net of tax (provision)/benefit	113	67
Current period change in OCI	(2,149)	4,372
Accumulated other comprehensive income loss, ending balance	(22,097)	15,377
Tax (provision) on amounts reclassified from AOCI for defined benefit plans	(60)	(37)
Net Unrealized Gain/(Loss) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, beginning balance	(13,726)	(8,316)
Other comprehensive income/(loss) before reclassifications	(7,003)	(4,349)
Amounts reclassified from accumulated other comprehensive loss, net of tax (provision)/benefit	7,937	(14,015)
Current period change in OCI	934	(18,364)
Accumulated other comprehensive income loss, ending balance	(12,792)	(26,680)
Tax (provision)/benefit on amounts reclassified from AOCI for cash flow hedges	$ (5,347)	$ 9,343