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Summary of Significant Accounting Policies (Tables) | 12 Months Ended
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Dec. 31, 2018
Policy Text Block [Abstract] |
Components of self-insurance reserves |
| December 31,
| 2018 |  | 2017
Self-insurance reserves (undiscounted) | $ | 157,538 |  |  | $ | 147,664 |
Self-insurance reserves (discounted) | 146,718 |  |  | 137,970 |

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- Definition Table containing amount of undiscounted and discounted self-insurance reserves the Company had at the balance sheet date. + References No definition available. + Details
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Namespace Prefix: | orly_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_PolicyTextBlockAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration