Name:	exas_AmortizationOfContributionLiability
Namespace Prefix:	exas_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Represents the amount outstanding as of the balance sheet date for amounts borrowed under the financing arrangement.

No definition available.

Name:	exas_FinancingArrangementAmountOutstanding
Namespace Prefix:	exas_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the proceeds from issuance of loan receivable to investor.

No definition available.

Name:	exas_NetProceedsFromFinancingArrangement
Namespace Prefix:	exas_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the period of recapture of the New Markets Tax Credits as provided in the Internal Revenue Code and applicable U.S. Treasury regulations.

No definition available.

Name:	exas_NewMarketTaxCreditsPeriodOfRecapture
Namespace Prefix:	exas_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the charge against earnings during the period for commitment fees and debt issuance expenses.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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

Name:	us-gaap_TransactionTypeAxis=exas_NewMarketTaxCreditProgramMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_CounterpartyNameAxis=exas_UnrelatedThirdPartyFinancialInstitutionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: