FAIR VALUE MEASUREMENTS - Schedule of Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Fair value measurements
Equity securities	$ 2,745	$ 5,149
Non-marketable securities	9,057	10,065
Contingent consideration	293,777	306,927
Fair Value, Recurring
Fair value measurements
Restricted cash	297	297
Equity securities	2,745	5,149
Non-marketable securities	9,057	10,065
Contingent consideration		306,927
Contingent consideration	(293,777)
Total	449,983	335,492
Fair Value, Recurring \| Corporate bonds
Fair value measurements
Estimated Fair Value	55,110	114,671
Fair Value, Recurring \| Commercial paper
Fair value measurements
Estimated Fair Value	8,902
Fair Value, Recurring \| U.S. government agency securities
Fair value measurements
Estimated Fair Value	42,932	225,223
Fair Value, Recurring \| Asset backed securities
Fair value measurements
Estimated Fair Value	30,105	44,521
Fair Value, Recurring \| Cash and money market
Fair value measurements
Cash and cash equivalents, fair value	543,316	178,168
Fair Value, Recurring \| Commercial paper
Fair value measurements
Cash and cash equivalents, fair value	49,806	63,021
Fair Value, Recurring \| U.S. government agency securities
Fair value measurements
Cash and cash equivalents, fair value	1,490	1,304
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fair Value, Recurring
Fair value measurements
Restricted cash	297	297
Equity securities	2,745	5,149
Non-marketable securities	0	0
Contingent consideration		0
Contingent consideration	0
Total	546,358	183,614
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fair Value, Recurring \| Corporate bonds
Fair value measurements
Estimated Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fair Value, Recurring \| Commercial paper
Fair value measurements
Estimated Fair Value	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fair Value, Recurring \| U.S. government agency securities
Fair value measurements
Estimated Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fair Value, Recurring \| Asset backed securities
Fair value measurements
Estimated Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fair Value, Recurring \| Cash and money market
Fair value measurements
Cash and cash equivalents, fair value	543,316	178,168
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fair Value, Recurring \| Commercial paper
Fair value measurements
Cash and cash equivalents, fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fair Value, Recurring \| U.S. government agency securities
Fair value measurements
Cash and cash equivalents, fair value	0	0
Significant Other Observable Inputs (Level 2) \| Fair Value, Recurring
Fair value measurements
Restricted cash	0	0
Equity securities	0	0
Non-marketable securities	0	0
Contingent consideration		0
Contingent consideration	0
Total	188,345	448,740
Significant Other Observable Inputs (Level 2) \| Fair Value, Recurring \| Corporate bonds
Fair value measurements
Estimated Fair Value	55,110	114,671
Significant Other Observable Inputs (Level 2) \| Fair Value, Recurring \| Commercial paper
Fair value measurements
Estimated Fair Value	8,902
Significant Other Observable Inputs (Level 2) \| Fair Value, Recurring \| U.S. government agency securities
Fair value measurements
Estimated Fair Value	42,932	225,223
Significant Other Observable Inputs (Level 2) \| Fair Value, Recurring \| Asset backed securities
Fair value measurements
Estimated Fair Value	30,105	44,521
Significant Other Observable Inputs (Level 2) \| Fair Value, Recurring \| Cash and money market
Fair value measurements
Cash and cash equivalents, fair value	0	0
Significant Other Observable Inputs (Level 2) \| Fair Value, Recurring \| Commercial paper
Fair value measurements
Cash and cash equivalents, fair value	49,806	63,021
Significant Other Observable Inputs (Level 2) \| Fair Value, Recurring \| U.S. government agency securities
Fair value measurements
Cash and cash equivalents, fair value	1,490	1,304
Significant Unobservable Inputs (Level 3) \| Fair Value, Recurring
Fair value measurements
Restricted cash	0	0
Equity securities	0	0
Non-marketable securities	9,057	10,065
Contingent consideration		306,927
Contingent consideration	(293,777)
Total	(284,720)	(296,862)
Significant Unobservable Inputs (Level 3) \| Fair Value, Recurring \| Corporate bonds
Fair value measurements
Estimated Fair Value	0	0
Significant Unobservable Inputs (Level 3) \| Fair Value, Recurring \| Commercial paper
Fair value measurements
Estimated Fair Value	0
Significant Unobservable Inputs (Level 3) \| Fair Value, Recurring \| U.S. government agency securities
Fair value measurements
Estimated Fair Value	0	0
Significant Unobservable Inputs (Level 3) \| Fair Value, Recurring \| Asset backed securities
Fair value measurements
Estimated Fair Value	0	0
Significant Unobservable Inputs (Level 3) \| Fair Value, Recurring \| Cash and money market
Fair value measurements
Cash and cash equivalents, fair value	0	0
Significant Unobservable Inputs (Level 3) \| Fair Value, Recurring \| Commercial paper
Fair value measurements
Cash and cash equivalents, fair value	0	0
Significant Unobservable Inputs (Level 3) \| Fair Value, Recurring \| U.S. government agency securities
Fair value measurements
Cash and cash equivalents, fair value	$ 0	$ 0

Restricted Cash, Fair Value Disclosure

No definition available.

Name:	exas_RestrictedCashFairValueDisclosure
Namespace Prefix:	exas_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481830/320-10-45-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479853/942-210-S99-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479130/326-30-45-1

+ Details

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

- Definition

Amount of liability recognized arising from contingent consideration in a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479581/805-30-50-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479668/805-30-25-6

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 35
-Paragraph 1
-Subparagraph (b)
-SubTopic 30
-Topic 805
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479613/805-30-35-1

+ Details

Name:	us-gaap_BusinessCombinationContingentConsiderationLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of liability recognized arising from contingent consideration in a business combination, expected to be settled within one year or the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479668/805-30-25-6

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 35
-Paragraph 1
-Subparagraph b
-SubTopic 30
-Topic 805
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479613/805-30-35-1

+ Details

Name:	us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

No definition available.

+ Details

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

- Definition

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483467/210-10-45-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482736/825-10-45-1A

+ Details

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

- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-3

+ Details

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

- Definition

Fair value of asset after deduction of liability.

+ References

No definition available.

+ Details

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

- Definition

Value of the not readily marketable security or category which has been determined by management based upon fair value methods, including pricing of similar securities and valuation techniques and is included in the schedule of financial condition or the balance sheet.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 940
-SubTopic 820
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481753/940-820-50-1

+ Details

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

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_CashAndCashEquivalentsAxis=us-gaap_MoneyMarketFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CashAndCashEquivalentsAxis=us-gaap_CommercialPaperMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CashAndCashEquivalentsAxis=us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: