Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service.

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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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Amount of gain (loss) on sale or disposal of property, plant and equipment assets, including oil and gas property and timber property.

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Amount of divestiture of long-lived, physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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Balance Sheet Details - Property and Equipment (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment	$ 200.4	$ 262.9	$ 200.4
Less accumulated depreciation and amortization	(54.8)	(79.8)	(54.8)
Total property and equipment, net	145.6	183.1	145.6
Loss on disposal of machinery and equipment		5.4
Depreciation	16.1	28.6		$ 14.4
Building
Property, Plant and Equipment [Line Items]
Property and equipment	6.0	6.0	6.0
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment	5.7	9.0	5.7
Computer software and hardware
Property, Plant and Equipment [Line Items]
Property and equipment	25.6	29.2	25.6
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property and equipment	33.8	80.7	33.8
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	41.7	80.7	41.7
Less accumulated depreciation and amortization		(0.7)
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment	87.6	57.3	87.6
Disposal of property plant and equipment			11.0
Leased Buildings -232 South Dobson Road
Property, Plant and Equipment [Line Items]
Construction in progress	$ 33.6	$ 6.2	$ 33.6