Significant Accounting Policies - Long-lived assets (Details) $ in Millions	3 Months Ended
Apr. 04, 2020 USD ($)
Long-lived assets [Abstract]
Asset impairment charges	$ 2.5
Finite-Lived Intangible Assets \| Industrial Lasers & System
Long-lived assets [Abstract]
Asset impairment charges	33.9
Property and equipment \| Industrial Lasers & System
Long-lived assets [Abstract]
Asset impairment charges	85.6
Right-Of-Use Assets \| Industrial Lasers & System
Long-lived assets [Abstract]
Asset impairment charges	$ 1.8

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=123351718&loc=d3e2420-110228

Name:	us-gaap_AssetImpairmentCharges
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration