Accumulated Other Comprehensive Income/(Loss) AOCI Attributable to G&W (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income/(loss), beginning balance	$ (146,456)	$ (105,534)
Other comprehensive income/(loss) before reclassifications	(6,558)	10,550
Amounts reclassified from accumulated other comprehensive loss, net of tax (provision)/benefit	(431)	(205)
Current period change in OCI	(6,989)	10,345
United States Tax Cuts and Jobs Act 2017, Reclassification from AOCL to Retained Earnings		0
Accumulated other comprehensive income/(loss), ending balance	(153,445)	(98,159)
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income/(loss), beginning balance	(144,503)	(74,617)
Other comprehensive income/(loss) before reclassifications	5,432	3,401
Amounts reclassified from accumulated other comprehensive loss, net of tax (provision)/benefit	0	0
Current period change in OCI	5,432	3,401
United States Tax Cuts and Jobs Act 2017, Reclassification from AOCL to Retained Earnings		0
Accumulated other comprehensive income/(loss), ending balance	(139,071)	(71,216)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income/(loss), beginning balance	11,120	(19,601)
Other comprehensive income/(loss) before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive loss, net of tax (provision)/benefit	(216)	43
Current period change in OCI	(216)	43
United States Tax Cuts and Jobs Act 2017, Reclassification from AOCL to Retained Earnings		(132)
Accumulated other comprehensive income/(loss), ending balance	10,904	(19,690)
Tax (provision) on amounts reclassified from AOCL for defined benefit plans	89	(14)
Net Unrealized Gain/(Loss) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income/(loss), beginning balance	(13,073)	(11,316)
Other comprehensive income/(loss) before reclassifications	(11,990)	7,149
Amounts reclassified from accumulated other comprehensive loss, net of tax (provision)/benefit	(215)	(248)
Current period change in OCI	(12,205)	6,901
United States Tax Cuts and Jobs Act 2017, Reclassification from AOCL to Retained Earnings		(2,838)
Accumulated other comprehensive income/(loss), ending balance	(25,278)	(7,253)
Tax (provision)/benefit on amounts reclassified from AOCL for cash flow hedges	91	89
AOCL Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Current period change in OCI	$ (6,989)	10,345
United States Tax Cuts and Jobs Act 2017, Reclassification from AOCL to Retained Earnings		$ (2,970)

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