Other Financial Statements Details Inventories (Details) - USD ($) $ in Millions	Jun. 30, 2018	Apr. 01, 2018	Mar. 31, 2018
Accounts Receivable, Net [Abstract]
Raw materials	$ 74.1		$ 26.0
Work in process	685.2		311.8
Finished goods	345.5		138.4
Total inventories	1,104.8	$ 471.1	476.2
Inventory [Line Items]
Inventories	1,104.8	$ 471.1	$ 476.2
Microsemi Corporation \| Fair Value Adjustment to Inventory
Accounts Receivable, Net [Abstract]
Total inventories	309.7
Inventory [Line Items]
Inventories	$ 309.7

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Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of merchandise or goods held by the company that are readily available for sale.

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Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

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Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of unprocessed items to be consumed in the manufacturing or production process.

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Carrying amount, net of reserves and adjustments, as of the balance sheet date of merchandise or goods which are partially completed. This inventory is generally comprised of raw materials, labor and factory overhead costs, which require further materials, labor and overhead to be converted into finished goods, and which generally require the use of estimates to determine percentage complete and pricing.

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