Income Taxes - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
	Dec. 31, 2017	Nov. 17, 2018	Nov. 18, 2017	Jul. 25, 2018
Income Tax Disclosure [Abstract]
Effective tax rate		21.70%	34.60%
U.S. corporate income tax rate	35.00%	21.00%
Tax benefit from reduction of U.S. statutory rate		$ 52.6
Additional Excess tax benefits from stock option exercises compared to prior year		9.0
Tax benefit resulting from stock option accounting		$ 11.2	$ 2.2
One-time mandatory transition tax				$ 25.8
Tax expense due to remeasurement of net U.S. federal deferred tax liability				$ 157.3