Name:	saft_AvailableForSaleSecuritiesIncludingRealEstateInvestmentTrust
Namespace Prefix:	saft_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The required advance notice before quarter end so that the entity may dispose of an equity security investment which has a fair value determined using the trust's net asset value.

No definition available.

Name:	saft_EquityInvestmentRequiredAdvanceNoticePeriodToDispose
Namespace Prefix:	saft_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Transfers of assets amount measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

No definition available.

Name:	saft_FairValueAssetsLevel1ToLevel2TransfersAmount1
Namespace Prefix:	saft_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Ttransfers of assets amount measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1.

No definition available.

Name:	saft_FairValueAssetsLevel2ToLevel1TransfersAmount1
Namespace Prefix:	saft_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents number of level 3 securities held by the company.

No definition available.

Name:	saft_Level3SecuritiesHeldNumber
Namespace Prefix:	saft_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Fair value of investment other than investment in equity security, investment in debt security and equity method investment. Includes, but is not limited to, investment in certain entities that calculate net asset value per share. Example includes, but is not limited to, investment in hedge fund, venture capital fund, private equity fund, and real estate partnership or fund.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 6A
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=SL6742756-110258

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 35
-Paragraph 54B
-URI https://asc.fasb.org/extlink&oid=126972413&loc=SL7495116-110257

Name:	us-gaap_AlternativeInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of investment in marketable security.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.4)
-URI https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878

Name:	us-gaap_MarketableSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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.