Fair Value Measurements (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Fair Value Measurements
Transfers between levels of the hierarchy	$ 0	$ 0	$ 0	$ 0

The amount of transfers of assets or liabilities measured on either a recurring or nonrecurring basis between Levels 1, 2 or 3 which have taken place during the period.

No definition available.

Name:	orly_FairValueTransfersBetweenLevelsTotal
Namespace Prefix:	orly_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration