Derivative Hedging Instruments (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018
Derivative, Notional Amount	$ 0	$ 0
Derivative Instruments Weighted Average Interest Rate Received Paid	0.00%	0.00%
Increase Decrease In Interest Expense	$ 0	$ 0
Derivative Financial Instruments, Assets [Member] \| Swap [Member]
Derivative, Swap Type	FAIR VALUE	FAIR VALUE
Derivative Asset, Notional Amount	$ 22,628	$ 16,681
Derivative Instruments Weighted Average Interest Rate Received Paid	4.78%	4.04%
Derivative Instruments, Repricing Frequency	MONTHLY	MONTHLY
Increase (Decrease) in Fair Value of Interest Rate Fair Value Hedging Instruments	$ 16	$ (33)
Derivative Financial Instruments, Liabilities [Member] \| Swap [Member]
Derivative, Swap Type	FAIR VALUE	FAIR VALUE
Derivative Liability, Notional Amount	$ (22,628)	$ (16,681)
Derivative Instruments Weighted Average Interest Rate Received Paid	(4.78%)	(4.04%)
Derivative Instruments, Repricing Frequency	MONTHLY	MONTHLY
Increase (Decrease) in Fair Value of Interest Rate Fair Value Hedging Instruments	$ (16)	$ 33

Description for repricing frequency of derivative instruments.

No definition available.

Name:	asrv_DerivativeInstrumentsRepricingFrequency
Namespace Prefix:	asrv_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of interest received(Paid) during the period under Interest Rate swap transaction.

+ References

No definition available.

+ Details

Name:	asrv_DerivativeInstrumentsWeightedAverageInterestRateReceivedPaid
Namespace Prefix:	asrv_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

This amount represents the increase (decrease) in interest expense (not fair value) of interest rate swaps.

+ References

No definition available.

+ Details

Name:	asrv_IncreaseDecreaseInInterestExpense
Namespace Prefix:	asrv_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Nominal or face amount used to calculate payments on the derivative asset.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

+ Details

Name:	us-gaap_DerivativeAssetNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Nominal or face amount used to calculate payments on the derivative liability.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

+ Details

Name:	us-gaap_DerivativeLiabilityNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Indicates whether the entity pays a variable or fixed price on a price risk swap.

+ References

No definition available.

+ Details

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

- Definition

Amount of unrealized gain (loss) related to the fair value of interest rate derivatives designated as fair value hedging instruments, as offset by the gain (loss) on the hedged item to the extent that the fair value hedge is determined to be effective.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959

+ Details

Name:	us-gaap_IncreaseDecreaseInFairValueOfInterestRateFairValueHedgingInstruments1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_DerivativeFinancialInstrumentsAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_SwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: