Summary of Significant Accounting Policies - Insurance and Derivatives (Details) $ in Millions	12 Months Ended
Dec. 26, 2019 USD ($)
Insurance Loss Reserves [Abstract]
Maximum loss before additional coverage applies	$ 10.0

Maximum amount of loss before stop-loss insurance recoveries.

No definition available.

Name:	fnd_MaximumLossBeforeAdditionalCoverageApplies
Namespace Prefix:	fnd_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration