Commitments and Contingencies (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Commitments and Contingencies
Legal defense accrual		$ 6,500
Legal defense accrual reversal	$ 6,500
Limited partnership commitments
Commitments and Contingencies
Investment in limited partnership, committed amount	160,000
Contribution made	114,418
Contributions to be made	$ 52,000

Represents the committed amount of investment in limited partnership made by the company.

No definition available.

Name:	saft_InvestmentInLimitedPartnershipCommittedAmount
Namespace Prefix:	saft_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the amount of contribution made by the company to the limited partnership investment.

+ References

No definition available.

+ Details

Name:	saft_LimitedPartnershipInvestmentMade
Namespace Prefix:	saft_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the amount of remaining committed capital due to be called.

+ References

No definition available.

+ Details

Name:	saft_LimitedPartnershipInvestmentToBeMade
Namespace Prefix:	saft_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of loss contingency liability accrual reversal.

+ References

No definition available.

+ Details

Name:	saft_LossContingencyAccrualReversal
Namespace Prefix:	saft_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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

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

- Definition

Amount of loss contingency liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=121557415&loc=d3e14326-108349

Reference 2: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 10
-URI https://asc.fasb.org/extlink&oid=121557415&loc=d3e14615-108349

+ Details

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

- Details

Name:	us-gaap_TypeOfArrangementAxis=us-gaap_CommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: