Accumulated Other Comprehensive Income (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated other comprehensive income, beginning balance	$ (72,252,000)	$ (153,457,000)	$ (72,252,000)
Other comprehensive (loss)/income, before reclassifications		(72,726,000)	(79,524,000)
Amounts reclassified from accumulated other comprehensive income, net of tax		14,847,000	(1,681,000)
Other Comprehensive Income (Loss), Net of Tax		(83,968,000)	(81,205,000)	$ (78,341,000)
Other comprehensive income/(loss) attributable to G&W		(57,879,000)
Accumulated other comprehensive income, ending balance		(211,336,000)	(153,457,000)	(72,252,000)
Net (loss)/income attributable to noncontrolling interest		(41,000)	0	251,000
Foreign currency translation adjustment, Net of tax, Attributable to noncontrolling interest		8,805,000	0	0
Unrealized loss on qualifying cash flow hedges,Net of tax, Attributable to noncontrolling interest		(256,000)	0	0
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	0	8,508,000	0	251,000
Tax benefit on derivative amount attributable to noncontrolling interest		110,000
Defined Benefit Plan [Member]
Accumulated other comprehensive income, beginning balance	1,405,000	11,005,000	1,405,000
Other comprehensive (loss)/income, before reclassifications		(31,155,000)	9,526,000
Amounts reclassified from accumulated other comprehensive income, net of tax		202,000	74,000
Other Comprehensive Income (Loss), Net of Tax			9,600,000
Other comprehensive income/(loss) attributable to G&W		(30,953,000)
Accumulated other comprehensive income, ending balance		(19,948,000)	11,005,000	1,405,000
Tax provision on pension amounts reclassified from AOCI		(113,000)	(41,000)
Net Unrealized Gain/(Loss) on Cash Flow Hedges [Member]
Accumulated other comprehensive income, beginning balance	(2,911,000)	(8,316,000)	(2,911,000)
Other comprehensive (loss)/income, before reclassifications		14,583,000	(3,650,000)
Amounts reclassified from accumulated other comprehensive income, net of tax		(19,993,000)	(1,755,000)
Other Comprehensive Income (Loss), Net of Tax			(5,405,000)
Other comprehensive income/(loss) attributable to G&W		(5,410,000)
Accumulated other comprehensive income, ending balance		(13,726,000)	(8,316,000)	(2,911,000)
Tax benefit on derivative amounts reclassified from AOCI		11,637,000	1,170,000
Cumulative Foreign Currency Translation Adjustment [Member]
Accumulated other comprehensive income, beginning balance	$ (70,746,000)	(156,146,000)	(70,746,000)
Other comprehensive (loss)/income, before reclassifications		(56,154,000)	(85,400,000)
Amounts reclassified from accumulated other comprehensive income, net of tax		34,638,000	0
Other Comprehensive Income (Loss), Net of Tax			(85,400,000)
Other comprehensive income/(loss) attributable to G&W		(21,516,000)
Accumulated other comprehensive income, ending balance		(177,662,000)	$ (156,146,000)	$ (70,746,000)
Tax benefit on foreign currency amounts reclassified from AOCI		$ 0