Intangible Assets - Summary of Significant Goodwill Amounts (Detail) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Disclosure of information for cash-generating units [Line Items]
Goodwill allocated to the cash-generating unit at balance sheet date	€ 6,905	€ 7,396
United Kingdom Cash Generating Units [member]
Disclosure of information for cash-generating units [Line Items]
Goodwill allocated to the cash-generating unit at balance sheet date	€ 725	€ 748
Discount rate applied to the cash flow projections (real pre-tax)	7.60%	7.80%
Average EBITDA (as defined)* margin over the initial 5-year period	13.90%	13.70%
Value-in-use (present value of future cash flows)	€ 3,221	€ 3,549
Excess of value-in-use over carrying amount	1,334	1,338
Oldcastle Building Products Cash Generating Units [member]
Disclosure of information for cash-generating units [Line Items]
Goodwill allocated to the cash-generating unit at balance sheet date	€ 1,555	€ 1,670
Discount rate applied to the cash flow projections (real pre-tax)	10.30%	11.70%
Average EBITDA (as defined)* margin over the initial 5-year period	15.10%	14.40%
Value-in-use (present value of future cash flows)	€ 5,628	€ 4,695
Excess of value-in-use over carrying amount	€ 2,152	€ 1,388

Average EBITDA margin over initial five year period.

No definition available.

Name:	crh_AverageEBITDAMarginOverInitialFiveYearPeriod
Namespace Prefix:	crh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount by which a cash-generating unit's (group of units') recoverable amount exceeds its carrying amount. [Refer: Carrying amount [member]; Cash-generating units [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 36
-IssueDate 2016-01-13
-Paragraph 134
-Subparagraph f
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=36&date=2016-03-30&anchor=para_134_f_i&doctype=Standard
-URIDate 2016-03-31

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 36
-IssueDate 2016-01-13
-Paragraph 135
-Subparagraph e
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=36&date=2016-03-30&anchor=para_135_e_i&doctype=Standard
-URIDate 2016-03-31

+ Details

Name:	ifrs-full_AmountByWhichUnitsRecoverableAmountExceedsItsCarryingAmount
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The discount rate applied to cash flow projections for a cash-generating unit (group of units). [Refer: Cash-generating units [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 36
-IssueDate 2016-01-13
-Paragraph 134
-Subparagraph d
-Clause v
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=36&date=2016-03-30&anchor=para_134_d_v&doctype=Standard
-URIDate 2016-03-31

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 36
-IssueDate 2016-01-13
-Paragraph 134
-Subparagraph e
-Clause v
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=36&date=2016-03-30&anchor=para_134_e_v&doctype=Standard
-URIDate 2016-03-31

+ Details

Name:	ifrs-full_DescriptionOfDiscountRatesAppliedToCashFlowProjections
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

Name:	ifrs-full_DisclosureOfInformationForIndividualAssetOrCashgeneratingUnitWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of assets representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognised. [Refer: Business combinations [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 3
-IssueDate 2016-01-13
-Paragraph B67
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=3&date=2016-03-30&anchor=para_B67_d&doctype=Appendix&seq=2
-URIDate 2016-03-31

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 36
-IssueDate 2016-01-13
-Paragraph 134
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=36&date=2016-03-30&anchor=para_134_a&doctype=Standard
-URIDate 2016-03-31

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 36
-IssueDate 2016-01-13
-Paragraph 135
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=36&date=2016-03-30&anchor=para_135_a&doctype=Standard
-URIDate 2016-03-31

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2016-01-13
-Paragraph 54
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2016-03-30&anchor=para_54_c&doctype=Standard
-URIDate 2016-03-31

+ Details

Name:	ifrs-full_Goodwill
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The higher of an asset’s (or cash-generating unit’s) fair value less costs of disposal and its value in use. [Refer: Cash-generating units [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 36
-IssueDate 2016-01-13
-Paragraph 130
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=36&date=2016-03-30&anchor=para_130_e&doctype=Standard
-URIDate 2016-03-31

+ Details

Name:	ifrs-full_RecoverableAmountOfAssetOrCashgeneratingUnit
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	ifrs-full_IndividualAssetsOrCashgeneratingUnitsWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesAxis=crh_UnitedKingdomCashGeneratingUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_IndividualAssetsOrCashgeneratingUnitsWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesAxis=crh_OldcastleBuildingProductsCashGeneratingUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: