Debt and Financing Arrangements - Schedule of Principal Maturities of Long-Term Debt Including Interest On Finance Leases (Detail) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Debt Instruments [Abstract]
2025	$ 1,138
2026	991
2027	0
2028	0
2029	307,000
Thereafter	0
Total	309,129
Less: Amounts Representing Interest on Finance Leases	38
Total	$ 309,091	$ 200,294

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

- Definition

Long term debt and finance lease liability including interest on finance leases.

+ References

No definition available.

+ Details

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

- Definition

Principal amount of long-term debt and finance lease liability maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

No definition available.

+ Details

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

- Definition

Principal amount of long-term debt and finance lease liability maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

No definition available.

+ Details

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

- Definition

Principal amount of long-term debt and finance lease liability maturing in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

No definition available.

+ Details

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

- Definition

Principal amount of long-term debt and finance lease liability maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

No definition available.

+ Details

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

- Definition

Principal amount of long-term debt and finance lease liability maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

No definition available.

+ Details

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

- Definition

Amount of long-term debt and finance lease liability maturing in the remainder of the fiscal year following the latest fiscal year ended.

+ References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount of lessee's undiscounted obligation for lease payments in excess of discounted obligation for lease payments for finance lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-6

+ Details

Name:	us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant