Related Party Transactions (Detail) (USD $)	1 Months Ended	12 Months Ended	168 Months Ended
May 31, 2001	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014
Related Party Transactions [Abstract]
Loan agreement	$ 26,500,000
Impairment charges against loan					15,700,000sfe_LoanImpairmentCharge
Receipt in payments on loan		100,000us-gaap_ProceedsFromRelatedPartyDebt	0us-gaap_ProceedsFromRelatedPartyDebt	0us-gaap_ProceedsFromRelatedPartyDebt	17,000,000us-gaap_ProceedsFromRelatedPartyDebt
Loan, carrying value		$ 0sfe_ImpairedLoansCarryingAmount			$ 0sfe_ImpairedLoansCarryingAmount

Amount of transactions with related party during the financial reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39622-107864

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39603-107864

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Name:	us-gaap_RelatedPartyTransactionAmountsOfTransaction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration