Condensed Consolidated Statements of Equity - USD ($) shares in Millions, $ in Millions	Total	Ordinary Shares	Additional Paid In Capital	Accumulated Deficit	Unrealized Hedging (Losses) Gains	Foreign Currency Translation	Defined Benefit Plans	Total Accumulated Other Comprehensive Loss, net of tax
Beginning Balance (in shares) at Dec. 31, 2016		143.1
Beginning balance at Dec. 31, 2016	$ 590.0	$ 1,430.8	$ 252.4	$ (944.7)	$ 17.4	$ (155.5)	$ (10.4)	$ (148.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share issuances (in shares)		1.3
Share issuances	11.4	$ 12.9	(1.5)
Net loss	(245.6)			(245.6)
Stock-based compensation	33.5		33.5
Foreign currency translation	53.6					53.6		53.6
Defined benefit plans actuarial gain	0.3						0.3	0.3
Unrealized gain (loss) on hedging instruments	(23.7)				(23.7)			(23.7)
Amounts reclassified from AOCI to the statement of operations	11.4				11.4			11.4
Ending Balance (in shares) at Sep. 30, 2017		144.4
Ending balance at Sep. 30, 2017	430.9	$ 1,443.7	284.4	(1,190.3)	5.1	(101.9)	(10.1)	(106.9)
Beginning balance at Jun. 30, 2017					3.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(78.6)
Foreign currency translation	13.2
Ending Balance (in shares) at Sep. 30, 2017		144.4
Ending balance at Sep. 30, 2017	430.9	$ 1,443.7	284.4	(1,190.3)	5.1	(101.9)	(10.1)	(106.9)
Beginning Balance (in shares) at Dec. 31, 2017		145.1
Beginning balance at Dec. 31, 2017	503.9	$ 1,451.3	305.0	(1,165.2)	19.6	(101.1)	(5.7)	(87.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Capital reduction	0.0	$ (1,436.7)	1,436.7
Share issuances (in shares)		1.3
Share issuances	8.9	$ 0.1	8.8
Net loss	(172.9)			(172.9)
Stock-based compensation	54.4		54.4
Foreign currency translation	(38.0)					(38.0)		(38.0)
Defined benefit plans actuarial gain	0.2						0.2	0.2
Unrealized gain (loss) on hedging instruments	38.6				38.6			38.6
Amounts reclassified from AOCI to the statement of operations	(12.4)				(12.4)			(12.4)
Proceeds from IPO and Concurrent Private Placement, net of underwriting and other expenses (in shares)		62.3
Proceeds from IPO and Concurrent Private Placement, net of underwriting and other expenses	993.9	$ 6.2	987.7
Other activity	(3.4)		(3.4)
Ending Balance (in shares) at Sep. 30, 2018		208.7
Ending balance at Sep. 30, 2018	1,409.1	$ 20.9	2,789.2	(1,302.2)	45.8	(139.1)	(5.5)	(98.8)
Beginning balance at Jun. 30, 2018					41.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(48.7)
Foreign currency translation	(12.4)
Ending Balance (in shares) at Sep. 30, 2018		208.7
Ending balance at Sep. 30, 2018	$ 1,409.1	$ 20.9	$ 2,789.2	$ (1,302.2)	$ 45.8	$ (139.1)	$ (5.5)	$ (98.8)