Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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

No definition available.

+ Details

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

- Definition

Amount of the required periodic payments applied to principal.

+ References

+ Details

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

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28555-108399

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Amount of long-term debt and capital lease obligation due after one year or beyond the normal operating cycle, if longer.

+ References

+ Details

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

- Definition

Amount of long-term debt and capital leases due within one year or the normal operating cycle, if longer.

+ References

+ Details

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

- Definition

Amount of long-term debt and capital lease obligations including current maturities.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dci_ThreePointSevenTwoPercentUnsecuredSeniorNotesDueMarchTwentySevenTwoThousandTwentyFourMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dci_UnsecuredSeniorNotesFiveMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dci_UnsecuredSeniorNotesSixMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dci_VariableRateGuaranteedSeniorNoteDueMayNineteenTwoThousandNineteenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dci_VariableRateGuaranteedSeniorNoteDueJulyFifteenTwoThousandTwentyOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dci_VariableRateCommittedRevolvingCreditFacilityDueJulyTwentyFirstTwoThousandTwentyTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_UnsecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dci_VariableRateCommittedUnsecuredTermLoanDueJulyTwentyFirstTwoThousandTwentyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_CapitalLeaseObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dci_CapitalizedLeaseObligationsAndOtherWithVariousMaturityDatesAndInterestRatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Long-Term Debt (Schedule of Long-term Debt) (Details) ¥ in Millions	12 Months Ended
	Jul. 31, 2019 JPY (¥)	Jul. 31, 2019 USD ($)	Jul. 31, 2019 USD ($)	Jul. 31, 2018 JPY (¥)	Jul. 31, 2018 USD ($)
Debt Instrument [Line Items]
Debt issuance costs, net			$ (1,500,000)		$ (1,900,000)
Subtotal			634,600,000		514,900,000
Less: current maturities			(50,200,000)		(15,300,000)
Long-term debt			584,400,000		499,600,000
Senior Notes \| 3.72% Unsecured senior notes, interest payable semi-annually, principal payment of $125.0 million due March 27, 2024
Debt Instrument [Line Items]
Long-term debt, gross			$ 125,000,000		125,000,000
Debt instrument interest rate	3.72%		3.72%
Debt instrument periodic principal payment		$ 125,000,000
Senior Notes \| 2.93% Unsecured senior notes, interest payable semi-annually, principal payment of $25.0 million due April 16, 2025
Debt Instrument [Line Items]
Long-term debt, gross			$ 25,000,000		25,000,000
Debt instrument interest rate	2.93%		2.93%
Debt instrument periodic principal payment		25,000,000
Senior Notes \| 3.18% Unsecured senior notes, interest payable semi-annually, principal payment of $125.0 million due June 17, 2030
Debt Instrument [Line Items]
Long-term debt, gross			$ 125,000,000		125,000,000
Debt instrument interest rate	3.18%		3.18%
Debt instrument periodic principal payment		$ 125,000,000
Senior Notes \| Variable rate guaranteed senior note, interest payable quarterly, principal payment of ¥1.65 billion due May 20, 2024 and an interest rate of 0.41% as of July 31, 2019
Debt Instrument [Line Items]
Long-term debt, gross \| ¥	¥ 15.2			¥ 14.8
Debt instrument interest rate	0.41%		0.41%
Debt instrument periodic principal payment \| ¥	¥ 1,650.0
Senior Notes \| Variable rate guaranteed senior note, interest payable quarterly, principal payment of ¥1.00 billion due July 15, 2021 and an interest rate of 0.26% as of July 31, 2019
Debt Instrument [Line Items]
Long-term debt, gross \| ¥	¥ 9.2			¥ 9.0
Debt instrument interest rate	0.26%		0.26%
Debt instrument periodic principal payment \| ¥	¥ 1,000.0
Line of credit \| Variable rate committed, unsecured $500.0 million revolving credit facility due July 21, 2022 and an interest rate of 2.55% as of July 31, 2019
Debt Instrument [Line Items]
Long-term debt, gross			$ 286,500,000		167,400,000
Debt instrument interest rate	2.55%		2.55%
Borrowing capacity			$ 500,000,000.0
Term loan \| Variable rate committed, unsecured $50.0 million term loan due July 21, 2020 and an interest rate of 3.55% as of July 31, 2019
Debt Instrument [Line Items]
Long-term debt, gross			$ 50,000,000		50,000,000
Debt instrument interest rate	3.55%		3.55%
Debt instrument, face amount			$ 50,000,000.0
Capital lease obligations \| Capitalized lease obligations, with various maturity dates and interest rates
Debt Instrument [Line Items]
Long-term debt, gross			$ 200,000		$ 600,000