Summary of Significant Accounting Policies (Components of Self-Insurance Reserves) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Summary of Significant Accounting Policies
Self insurance reserves undiscounted	$ 122,866	$ 116,696
Self insurance reserves discounted	$ 111,840	$ 106,011

The undiscounted portion of self insurance reserves as of the balance sheet date.

No definition available.

Name:	orly_SelfInsuranceReservesUndiscounted
Namespace Prefix:	orly_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant