Summary of Significant Accounting Policies - Estimated Future Amortization Expense (Detail) (USD $)	Sep. 30, 2014
Accounting Policies [Abstract]
2015	$ 637,000
2016	510,000
2017	369,000
2018	262,000
2019	146,000
2020	139,000
2021	136,000
2022	109,000
2023	58,000
2024	30,000
Total estimated future amortization of expense	$ 2,396,000essa_EstimatedAmortizationOfExpense

Estimated amortization of expense.

No definition available.

Name:	essa_EstimatedAmortizationOfExpense
Namespace Prefix:	essa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Finite lived intangible assets amortization expense year eight.

+ References

No definition available.

+ Details

Name:	essa_FiniteLivedIntangibleAssetsAmortizationExpenseYearEight
Namespace Prefix:	essa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Finite lived intangible assets amortization expense year eleven.

+ References

No definition available.

+ Details

Name:	essa_FiniteLivedIntangibleAssetsAmortizationExpenseYearEleven
Namespace Prefix:	essa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Finite lived intangible assets amortization expense year nine.

+ References

No definition available.

+ Details

Name:	essa_FiniteLivedIntangibleAssetsAmortizationExpenseYearNine
Namespace Prefix:	essa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Finite lived intangible assets amortization expense year seven.

+ References

No definition available.

+ Details

Name:	essa_FiniteLivedIntangibleAssetsAmortizationExpenseYearSeven
Namespace Prefix:	essa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Finite lived intangible assets amortization expense year six.

+ References

No definition available.

+ Details

Name:	essa_FiniteLivedIntangibleAssetsAmortizationExpenseYearSix
Namespace Prefix:	essa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Finite lived intangible assets amortization expense year ten.

+ References

No definition available.

+ Details

Name:	essa_FiniteLivedIntangibleAssetsAmortizationExpenseYearTen
Namespace Prefix:	essa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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

- Definition

Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during 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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

+ Details

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

- Definition

Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during 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

+ Details

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

- Definition

Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during 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

+ Details

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

- Definition

Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during 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

+ Details

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