Summary of significant accounting policies – Insurance Expense (Details) $ in Thousands	12 Months Ended
Feb. 03, 2018 USD ($)
Summary of significant accounting policies
Stop loss coverage per employee health claim	$ 350
Stop loss coverage per general liability claim	100
Stop loss coverage per workers compensation claim	$ 250

Stop loss coverage of workers compensation claims.

No definition available.

Name:	ulta_StopLossCoverageOfWorkersCompensationClaims
Namespace Prefix:	ulta_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration