Name:	saia_LongTermDebtAndFinanceLeaseLiabiliity
Namespace Prefix:	saia_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of long-term debt and finance leases due within one year or the normal operating cycle, if longer.

No definition available.

Name:	saia_LongTermDebtAndFinanceLeaseLiabilityCurrent
Namespace Prefix:	saia_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of long-term debt and finance lease liability including current maturities.

No definition available.

Name:	saia_LongTermDebtAndFinanceLeaseLiabilityIncludingCurrentMaturities
Namespace Prefix:	saia_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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.

No definition available.

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Present value of lessee's discounted obligation for lease payments from finance lease.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
-URI https://asc.fasb.org/extlink&oid=128292326&loc=SL77918701-209980

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123391704&loc=SL77918627-209977