Accumulated Other Comprehensive Income/(Loss) AOCI Attributbale to G&W (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, beginning balance	$ (105,534)	$ (197,316)
Other comprehensive income/(loss) before reclassifications	10,550	23,984
Amounts reclassified from accumulated other comprehensive loss, net of tax (provision)/benefit	(205)	(153)
Current period change in OCI	10,345	23,831
Accumulated other comprehensive income loss, ending balance	(98,159)	(173,485)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax, Portion Attributable to Noncontrolling Interest		252
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, beginning balance	(74,617)	(163,642)
Other comprehensive income/(loss) before reclassifications	3,401	23,630
Amounts reclassified from accumulated other comprehensive loss, net of tax (provision)/benefit	0	0
United States Tax Cuts and Jobs Act 2017, Reclassification from AOCI to Retained Earnings	0
Current period change in OCI	3,401	23,630
Accumulated other comprehensive income loss, ending balance	(71,216)	(140,012)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, beginning balance	(19,601)	(19,948)
Other comprehensive income/(loss) before reclassifications	0	(931)
Amounts reclassified from accumulated other comprehensive loss, net of tax (provision)/benefit	43	38
United States Tax Cuts and Jobs Act 2017, Reclassification from AOCI to Retained Earnings	(132)
Current period change in OCI	43	(893)
Accumulated other comprehensive income loss, ending balance	(19,690)	(20,841)
Tax (provision) on amounts reclassified from AOCI for defined benefit plans	(14)	(20)
Net Unrealized Gain/(Loss) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, beginning balance	(11,316)	(13,726)
Other comprehensive income/(loss) before reclassifications	7,149	1,285
Amounts reclassified from accumulated other comprehensive loss, net of tax (provision)/benefit	(248)	(191)
United States Tax Cuts and Jobs Act 2017, Reclassification from AOCI to Retained Earnings	(2,838)
Current period change in OCI	6,901	1,094
Accumulated other comprehensive income loss, ending balance	(7,253)	(12,632)
Tax (provision)/benefit on amounts reclassified from AOCI for cash flow hedges	89	$ 120
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
United States Tax Cuts and Jobs Act 2017, Reclassification from AOCI to Retained Earnings	$ (2,970)

United States Tax Cuts and Jobs Act 2017, Reclassification from AOCI to Retained Earnings

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