Summary of Significant Accounting Policies (Components of Self-Insurance Reserves) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Policy Text Block [Abstract]
Self-insurance reserves (undiscounted)	$ 132,879orly_SelfInsuranceReservesUndiscounted	$ 126,715orly_SelfInsuranceReservesUndiscounted
Self-insurance reserves (discounted)	$ 123,276orly_SelfInsuranceReservesDiscounted	$ 116,062orly_SelfInsuranceReservesDiscounted

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