Income Taxes - Reconciliation of Income Tax (Benefit) at U.S. Federal Statutory Rate to Company's Effective Tax Rate (Detail)	12 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 29, 2018
Increase (decrease) in tax resulting from:
Income tax (benefit) provision at federal statutory rate	21.00%	21.00%	24.50%
Loss on sale of Cynosure	(31.30%)	0.00%	0.00%
Domestic production activities deduction	0.00%	0.00%	3.10%
State income taxes, net of federal benefit	2.90%	0.70%	(0.70%)
U.S. tax on foreign earnings	2.60%	(2.10%)	0.10%
Internal restructuring	0.00%	3.80%	0.00%
Non-deductible goodwill	0.00%	0.00%	(39.40%)
Tax credits	(0.60%)	3.30%	1.90%
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Percent	0	(0.020)	0.827
Unrecognized tax benefits	0.00%	0.10%	(1.80%)
Compensation	0.40%	(0.80%)	(0.30%)
Foreign rate differential	(1.20%)	5.40%	5.20%
Change in deferred tax rate	(0.60%)	0.00%	(1.20%)
Change in valuation allowance	1.30%	(9.50%)	0.50%
Other	(0.10%)	(3.10%)	(1.00%)
Effective income tax rate	(10.80%)	21.00%	73.40%