Compensation Related Costs Disclosure [Line Items]

No definition available.

Name:	essa_CompensationRelatedCostsDisclosureLineItems
Namespace Prefix:	essa_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Option expiration period.

+ References

No definition available.

+ Details

Name:	essa_OptionExpirationPeriod
Namespace Prefix:	essa_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Outstanding nonvested restricted stock.

+ References

No definition available.

+ Details

Name:	essa_OutstandingNonvestedRestrictedStock
Namespace Prefix:	essa_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Share based compensation arrangement by share based payment award additional number of shares available for grant.

+ References

No definition available.

+ Details

Name:	essa_ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalNumberOfSharesAvailableForGrant
Namespace Prefix:	essa_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Share based compensation arrangement by share based payment award maximum units.

+ References

No definition available.

+ Details

Name:	essa_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumUnits
Namespace Prefix:	essa_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Share based compensation arrangement by share based payment award options expected future expense.

+ References

No definition available.

+ Details

Name:	essa_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpectedFutureExpense
Namespace Prefix:	essa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Share based compensation arrangement by share based payment award options remaining vesting period.

+ References

No definition available.

+ Details

Name:	essa_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsRemainingVestingPeriod
Namespace Prefix:	essa_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Stock option vesting period.

+ References

No definition available.

+ Details

Name:	essa_StockOptionVestingPeriod
Namespace Prefix:	essa_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

+ Details

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

- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Net number of non-option equity instruments granted to participants.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Gross number of share options (or share units) granted during the period.

+ References

No definition available.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of options vested.

+ References

No definition available.

+ Details

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_PlanNameAxis=essa_EquityIncentivePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=essa_TwentySixteenEquityIncentivePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=essa_TwoThousandThirteenPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=essa_TwoThousandFourteenPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=essa_TwoThousandFifteenPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=essa_MarchFourTwoThousandSixteenPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=essa_DecemberThirteenTwoThousandSixteenPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=essa_MarchTwentyNineTwoThousandSeventeenPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VestingAxis=us-gaap_ShareBasedCompensationAwardTrancheOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VestingAxis=us-gaap_ShareBasedCompensationAwardTrancheTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=essa_TwoThousandSixteenPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=essa_DecemberTwoThousandSixteenPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=essa_NonQualifiedStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=essa_IncentiveStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Equity Incentive Plan - Additional Information (Detail) - USD ($)								6 Months Ended
	Mar. 29, 2017	Dec. 13, 2016	Mar. 04, 2016	May 20, 2015	Jul. 22, 2014	Apr. 01, 2013	May 23, 2008	Mar. 31, 2017	Mar. 31, 2016
Compensation Related Costs Disclosure [Line Items]
Stock option granted								0
Option vesting period								5 years
Option expiration period								10 years
Share-based compensation expense								$ 145,000	$ 79,000
Equity Incentive Plan [Member]
Compensation Related Costs Disclosure [Line Items]
Common stock issuance, Grant								2,377,326
2016 Plan [Member]
Compensation Related Costs Disclosure [Line Items]
Common stock issuance, Grant								250,000
Further number of shares, grants								0
Stock Option [Member]
Compensation Related Costs Disclosure [Line Items]
Number of available shares								1,698,090
Restricted Stock [Member]
Compensation Related Costs Disclosure [Line Items]
Number of available shares								679,236
Restricted stock granted	3,296	20,675	23,491	21,843	19,880	30,000	590,320
Share-based compensation expense								$ 145,000	$ 79,000
Restricted Stock [Member] \| 2013 [Member]
Compensation Related Costs Disclosure [Line Items]
Restricted shares vesting period								18 months
Restricted Stock [Member] \| 2014 [Member]
Compensation Related Costs Disclosure [Line Items]
Restricted shares vesting period								39 months
Expected future expense								$ 32,000
Remaining vesting periods								6 months
Restricted Stock [Member] \| 2015 [Member]
Compensation Related Costs Disclosure [Line Items]
Restricted shares vesting period								40 months
Expected future expense								$ 123,000
Remaining vesting periods								1 year 6 months
Restricted Stock [Member] \| March 4, 2016 [Member]
Compensation Related Costs Disclosure [Line Items]
Restricted shares vesting period								43 months
Restricted Stock [Member] \| 12/13/16 [Member]
Compensation Related Costs Disclosure [Line Items]
Restricted shares vesting period								46 months
Restricted Stock [Member] \| March 29, 2017 [Member] \| Tranche One [Member]
Compensation Related Costs Disclosure [Line Items]
Restricted shares vesting period								42 months
Restricted shares vested, Number of shares								1,296
Expected future expense								$ 19,000
Remaining vesting periods								3 years 6 months
Outstanding nonvested restricted stock								1,296
Restricted Stock [Member] \| March 29, 2017 [Member] \| Tranche Two [Member]
Compensation Related Costs Disclosure [Line Items]
Restricted shares vesting period								18 months
Restricted shares vested, Number of shares								2,000
Expected future expense								$ 29,000
Remaining vesting periods								1 year 6 months
Outstanding nonvested restricted stock								2,000
Restricted Stock [Member] \| 2016 [Member]
Compensation Related Costs Disclosure [Line Items]
Expected future expense								$ 213,000
Remaining vesting periods								2 years 6 months
Restricted Stock [Member] \| December Two Thousand Sixteen Plan
Compensation Related Costs Disclosure [Line Items]
Expected future expense								$ 313,000
Remaining vesting periods								3 years 6 months
Non Qualified Stock Option [Member]
Compensation Related Costs Disclosure [Line Items]
Stock option granted							1,140,469
Incentive Stock Option [Member]
Compensation Related Costs Disclosure [Line Items]
Stock option granted							317,910