Business Acquisitions - Narrative (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended
	May 29, 2018	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2018	Jun. 30, 2018
Business Acquisition [Line Items]
Acquisition of Microsemi, net of cash acquired			$ 7,850.6	$ 0.0
Microsemi Corporation
Business Acquisition [Line Items]
Cash paid for shares	$ 8,190.0
Non cash consideration of certain share-based payment awards	53.9
Total consideration transferred	8,240.0
Liabilities assumed		$ 3,183.3	3,183.3		$ 3,223.7	$ 3,180.0
Payments to acquire businesses portion funded by additional line of credit borrowings	8,100.0
Transaction and other fees incurred in transaction	$ 22.0
Useful life (in years)	9 years
Deferred tax liabilities	$ 851.4
Net sales		477.6	1,097.8
Net income (loss)		$ (223.2)	$ (473.6)
Revolving credit facility | Microsemi Corporation
Business Acquisition [Line Items]
Payments to acquire businesses portion funded by additional line of credit borrowings	3,100.0
Term Loan Facility | Microsemi Corporation
Business Acquisition [Line Items]
Payments to acquire businesses portion funded by additional line of credit borrowings	3,000.0
Senior Secured Notes | Microsemi Corporation
Business Acquisition [Line Items]
Payments to acquire businesses portion funded by additional line of credit borrowings	2,000.0
Other Liabilities | Microsemi Corporation
Business Acquisition [Line Items]
Acquisition of Microsemi, net of cash acquired	$ 2,060.0