Minimum Term of Contract

No definition available.

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Namespace Prefix:	ghc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of Revenue Recognized During Period from Contract with Customer, Excluding Assessed Tax

+ References

No definition available.

+ Details

Name:	ghc_PercentageofRevenuefromContractwithCustomerExcludingAssessedTax
Namespace Prefix:	ghc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Revenue Remaining Performance Obligation Percentage of Revenue Expected to be Recognized Over Next 12 Months

+ References

No definition available.

+ Details

Name:	ghc_RevenueRemainingPerformanceObligationPercentageofRevenueExpectedtobeRecognizedOverNext12Months
Namespace Prefix:	ghc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, classified as noncurrent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=118944033&loc=SL49130533-203044

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130549-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118944033&loc=SL49130531-203044

+ Details

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

- Definition

Amount of revenue recognized that was previously reported as deferred or unearned revenue.

+ References

No definition available.

+ Details

Name:	us-gaap_DeferredRevenueRevenueRecognized1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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

No definition available.

+ Details

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

- Details

Name:	us-gaap_TimingOfTransferOfGoodOrServiceAxis=us-gaap_TransferredOverTimeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TimingOfTransferOfGoodOrServiceAxis=us-gaap_TransferredAtPointInTimeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=country_US
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	srt_StatementGeographicalAxis=us-gaap_NonUsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=ghc_KaplanInternationalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=ghc_TestPreparationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ContractWithCustomerDurationAxis=us-gaap_LongTermContractWithCustomerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Revenue from Contracts with Customers (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Deferred revenue recognized in period related to beginning balance	$ 188.7
Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Percentage of Revenue	73.00%	76.00%
Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Percentage of Revenue	27.00%	24.00%
U.S. [Member]
Disaggregation of Revenue [Line Items]
Percentage of Revenue	74.00%	75.00%
Non-US [Member]
Disaggregation of Revenue [Line Items]
Percentage of Revenue	26.00%	25.00%
Kaplan International [Member]
Disaggregation of Revenue [Line Items]
Contract with Customer, Asset, Net, Noncurrent	$ 5.7		$ 5.3
Test Preparation [Member] \| Long-term Contract with Customer [Member]
Disaggregation of Revenue [Line Items]
Minimum Term of Contract	12 months
Revenue Remaining Performance Obligation Percentage of Revenue Expected to be Recognized Over Next 12 Months	61.00%