Summary of Significant Accounting Policies (Components of Self-Insurance Reserves) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Summary of Significant Accounting Policies
Self-insurance reserves (undiscounted)	$ 116,696	$ 109,351
Self-insurance reserves (discounted)	$ 106,011	$ 99,612

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