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Income Taxes - Additional Information (Detail) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Dec. 31, 2017 | Jun. 29, 2019 | Jun. 30, 2018
Income Tax Disclosure [Line Items] |  |  |  |  |
U.S. federal corporate tax rate | 21.00% |  | 35.00% |  | 28.17%
Provisional tax expense |  |  |  |  | $ 41.4
One-time transition tax expense |  |  |  |  | 44.1
Benefit from remeasurement of deferred tax at new tax rate |  |  |  |  | 2.7
Increase in income tax iability, net of foreign tax and research credits | $ 11.6 |  |  |  |
Provision/(benefit) for income taxes | (0.3) | $ 3.2 |  |  |
Gross unrecognized tax benefits | 23.8 |  |  |  | 24.8
Gross unrecognized tax benefits increased (decreased) during the year | (1.0) |  |  |  |
Interest and penalties accrued related to unrecognized tax benefits | 2.0 |  |  |  |
Increase in interest and penalties accrued related to unrecognized tax benefits |  |  |  |  | $ 0.1
Maximum [Member] |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Estimated increase in unrecognized tax benefit in next twelve months | 4.3 |  |  |  |
Undistributed Foreign Earnings [Member] |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Provision/(benefit) for income taxes | $ 0.0 |  |  |  |
Cash Assets [Member] |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
One-time transition tax rate on post-1986 foreign earnings and profits | 15.50% |  |  |  |
Other Specified Assets [Member] |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
One-time transition tax rate on post-1986 foreign earnings and profits | 8.00% |  |  |  |
Scenario, Plan [Member] |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
U.S. federal corporate tax rate |  |  |  | 21.00% |

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