Investment and Mortgage-Backed Securities, Available for Sale (Schedule of Available for Sale Securities) (Details) (USD $)	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost of Investment And Mortgage-Backed Securities Available For Sale	$ 425,229,107	$ 420,876,924
Available-for-sale Securities, Gross Unrealized Gains	10,337,945	10,228,827
Available-for-sale Securities, Gross Unrealized Losses	1,064,423	1,405,211
Available-for-sale Securities, Fair Value Disclosure	434,502,629us-gaap_AvailableForSaleSecurities	429,700,540us-gaap_AvailableForSaleSecurities
FHLB Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost of Investment And Mortgage-Backed Securities Available For Sale	6,330,671	13,317,462
Available-for-sale Securities, Gross Unrealized Gains	55,934	83,691
Available-for-sale Securities, Gross Unrealized Losses	84,474	154,492
Available-for-sale Securities, Fair Value Disclosure		13,246,661
US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost of Investment And Mortgage-Backed Securities Available For Sale	2,000,000	5,750,000
Available-for-sale Securities, Gross Unrealized Gains	0	0
Available-for-sale Securities, Gross Unrealized Losses	14,978	82,006
Available-for-sale Securities, Fair Value Disclosure	1,985,022	5,667,994
US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost of Investment And Mortgage-Backed Securities Available For Sale	997,009	996,822
Available-for-sale Securities, Gross Unrealized Gains	15,425	7,559
Available-for-sale Securities, Gross Unrealized Losses	0	0
Available-for-sale Securities, Fair Value Disclosure	1,012,434	1,004,381
SBA Bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost of Investment And Mortgage-Backed Securities Available For Sale	118,078,000	106,637,400
Available-for-sale Securities, Gross Unrealized Gains	1,843,851	1,796,943
Available-for-sale Securities, Gross Unrealized Losses	217,508	307,649
Available-for-sale Securities, Fair Value Disclosure		108,126,694
Tax Exempt Municipal Bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost of Investment And Mortgage-Backed Securities Available For Sale	62,911,065	59,960,960
Available-for-sale Securities, Gross Unrealized Gains	2,061,707	2,579,543
Available-for-sale Securities, Gross Unrealized Losses	374,396	45,080
Available-for-sale Securities, Fair Value Disclosure		62,495,423
Mortgage-Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost of Investment And Mortgage-Backed Securities Available For Sale	234,661,924	233,963,842
Available-for-sale Securities, Gross Unrealized Gains	6,300,652	5,704,855
Available-for-sale Securities, Gross Unrealized Losses	373,067	815,984
Available-for-sale Securities, Fair Value Disclosure		238,852,713
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost of Investment And Mortgage-Backed Securities Available For Sale	250,438	250,438
Available-for-sale Securities, Gross Unrealized Gains	60,376	56,236
Available-for-sale Securities, Gross Unrealized Losses	0	0
Available-for-sale Securities, Fair Value Disclosure		$ 306,674

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (aa)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26610-111562

+ Details

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

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.2)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Amount of unrealized gain before deducting unrealized loss on investments in debt and equity securities classified as available-for-sale securities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGains
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of unrealized loss before deducting unrealized gain on investments in available-for-sale securities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

+ Details

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

- Details

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

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=sfdl_FederalFarmCreditSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=sfdl_SbaBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=sfdl_UsGovernmentSponsoredEnterprisesDebtSecuritiesFhlbSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_MortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: