Defined Benefit Plan, Mandatory Future Employer Contributions, Next Fiscal Year

No definition available.

Name:	gra_DefinedBenefitPlanMandatoryFutureEmployerContributionsNextFiscalYear
Namespace Prefix:	gra_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the percentage of certain specified foreign plan assets to total foreign plan assets.

+ References

No definition available.

+ Details

Name:	gra_DefinedBenefitPlanPercentageOfCertainSpecifiedForeignPlanAssetsToTotalForeignPlanAssets
Namespace Prefix:	gra_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the foreign pension plan assets, expressed as a percentage of global pension assets.

+ References

No definition available.

+ Details

Name:	gra_DefinedBenefitPlanPercentageOfForeignPlanAssetsToGlobalPensionAssets
Namespace Prefix:	gra_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

-- None. No documentation exists for this element. --

+ References

No definition available.

+ Details

Name:	gra_PlanContributionsAndFundingAbstract
Namespace Prefix:	gra_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(3)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of contributions expected to be received by defined benefit plan from employer in next fiscal year following latest fiscal year.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

+ Details

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

- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(01)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(01)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(ii)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=112275985&loc=d3e4179-114921

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(ii)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

+ Details

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

- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=112275985&loc=d3e4179-114921

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of actual investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Pension Plans and Other Retirement Plans (Details 4) - Pension Plans - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	$ 890.6	$ 1,131.3	$ 1,104.6
Domestic Plan [Member]
Pension plans and other postretirement benefit plans
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	100.00%
Percentage of Plan Assets	100.00%	100.00%
Assets Measured at Fair value	$ 871.1	$ 1,109.8	1,086.4
Expected return on plan assets	5.25%	5.50%
Plan contributions and funding
Defined Benefit Plan, Mandatory Future Employer Contributions, Next Fiscal Year	$ 0.1
Domestic Plan [Member] \| Defined Benefit Plan, Equity Securities, US [Member]
Pension plans and other postretirement benefit plans
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	9.00%
Percentage of Plan Assets	8.00%	11.00%
Domestic Plan [Member] \| Defined Benefit Plan, Equity Securities, Non-US [Member]
Pension plans and other postretirement benefit plans
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	4.00%
Percentage of Plan Assets	4.00%	5.00%
Domestic Plan [Member] \| Short Term Debt Securities [Member]
Pension plans and other postretirement benefit plans
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	4.00%
Percentage of Plan Assets	4.00%	10.00%
Domestic Plan [Member] \| Intermediate Debt Securities [Member]
Pension plans and other postretirement benefit plans
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	36.00%
Percentage of Plan Assets	36.00%	32.00%
Domestic Plan [Member] \| Long Term Debt Securities [Member]
Pension plans and other postretirement benefit plans
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	45.00%
Percentage of Plan Assets	46.00%	40.00%
Domestic Plan [Member] \| Other Investment [Member]
Pension plans and other postretirement benefit plans
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	2.00%
Percentage of Plan Assets	2.00%	2.00%
Domestic Plan [Member] \| Defined Benefit Plan, Common Collective Trust [Member]
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	$ 10.5	$ 10.2
Domestic Plan [Member] \| Annuity and immediate participation contracts
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	19.8	19.0
Domestic Plan [Member] \| Fair Value, Inputs, Level 1, 2 and 3 [Member]
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	30.3	29.2
Domestic Plan [Member] \| Fair Value, Inputs, Level 2 [Member]
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	30.3	29.2
Domestic Plan [Member] \| Fair Value, Inputs, Level 2 [Member] \| Defined Benefit Plan, Common Collective Trust [Member]
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	10.5	10.2
Domestic Plan [Member] \| Fair Value, Inputs, Level 2 [Member] \| Annuity and immediate participation contracts
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	19.8	19.0
Domestic Plan [Member] \| Fair Value Measured at Net Asset Value Per Share [Member]
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	840.8	1,080.6
Foreign Plan [Member]
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	$ 19.5	$ 21.5	$ 18.2
Percentage of foreign plan assets to global pension assets	2.00%	2.00%
Expected return on plan assets	4.69%	4.69%
Plan contributions and funding
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	$ 9.0
Foreign Plan [Member] \| Corporate bonds
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	0.4	$ 0.4
Foreign Plan [Member] \| Insurance contracts and other investments
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	0.4	0.3
Foreign Plan [Member] \| Cash
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	0.1
Foreign Plan [Member] \| Fair Value, Inputs, Level 1, 2 and 3 [Member]
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	0.9	0.7
Foreign Plan [Member] \| Fair Value, Inputs, Level 2 [Member]
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	0.8	0.7
Foreign Plan [Member] \| Fair Value, Inputs, Level 2 [Member] \| Corporate bonds
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	0.4	0.4
Foreign Plan [Member] \| Fair Value, Inputs, Level 2 [Member] \| Insurance contracts and other investments
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	0.4	0.3
Foreign Plan [Member] \| Fair Value, Inputs, Level 1 [Member]
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	0.1
Foreign Plan [Member] \| Fair Value, Inputs, Level 1 [Member] \| Cash
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	0.1
Foreign Plan [Member] \| Fair Value Measured at Net Asset Value Per Share [Member]
Pension plans and other postretirement benefit plans
Assets Measured at Fair value	$ 18.6	$ 20.8
Foreign Plan [Member] \| Canada
Pension plans and other postretirement benefit plans
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	100.00%
Percentage of Plan Assets	100.00%	100.00%
Defined Benefit Plan Percentage of Certain Specified foreign Plan Assets to Total Foreign Plan Assets	96.00%	97.00%
Expected return on plan assets	4.75%
Foreign Plan [Member] \| Canada \| Defined Benefit Plan, Equity Securities [Member]
Pension plans and other postretirement benefit plans
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	27.00%
Percentage of Plan Assets	28.00%	28.00%
Foreign Plan [Member] \| Canada \| Defined Benefit Plan, Debt Security [Member]
Pension plans and other postretirement benefit plans
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	58.00%
Percentage of Plan Assets	58.00%	58.00%
Foreign Plan [Member] \| Canada \| Other Investment [Member]
Pension plans and other postretirement benefit plans
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	15.00%
Percentage of Plan Assets	14.00%	14.00%
Foreign Plan [Member] \| Other country
Pension plans and other postretirement benefit plans
Defined Benefit Plan Percentage of Certain Specified foreign Plan Assets to Total Foreign Plan Assets	4.00%	3.00%