Beneficial ownership interest percentage.

No definition available.

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- Definition

Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Purchases during the period (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

+ References

No definition available.

+ Details

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- Definition

Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(e))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07.1(c))
-URI http://asc.fasb.org/extlink&oid=6488393&loc=d3e606610-122999

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- Details

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- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=sah_OilChemResearchCompanyMember
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- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=sah_SMISCHoldingsIncMember
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- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=sah_SpeedwayMotorsportsIncMember
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- Details

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Related Parties - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Sonic Financial Corporation [Member]
Related Party Transaction [Line Items]
Aggregate annual rent for leased aircraft usage	$ 0.4	$ 0.5	$ 0.6
Oil Chem Research Company [Member]
Related Party Transaction [Line Items]
Purchase from related party	1.9	2.1	2.1
SMISC Holdings, Inc. [Member]
Related Party Transaction [Line Items]
Purchase from related party	0.9	0.9	0.9
Speedway Motorsports, Inc. [Member]
Related Party Transaction [Line Items]
Vehicle sales to related party	$ 0.2	$ 0.2	$ 0.1
Minimum [Member] \| Mr. Marcus G. Smith [Member] \| Sonic Financial Corporation [Member]
Related Party Transaction [Line Items]
Ownership percentage	10.00%