Warranty (Details) (USD $)	9 Months Ended
Apr. 30, 2015	Apr. 30, 2014
Warranty [Abstract]
Beginning balance	$ 9,029,000us-gaap_ProductWarrantyAccrual	$ 10,526,000us-gaap_ProductWarrantyAccrual
Accruals for warranties issued during the reporting period	2,210,000	2,274,000
Accruals related to pre-existing warranties (including changes in estimates)	1,047,000	(452,000)
Less settlements made during the period	(3,706,000)us-gaap_ProductWarrantyAccrualPayments	(3,270,000)us-gaap_ProductWarrantyAccrualPayments
Ending balance	8,580,000us-gaap_ProductWarrantyAccrual	9,078,000us-gaap_ProductWarrantyAccrual
Specific warranty matters accrued	$ 0dci_SpecificWarrantyMattersAccrued	$ 0dci_SpecificWarrantyMattersAccrued

Specific Warranty Matters Accrued

No definition available.

Name:	dci_SpecificWarrantyMattersAccrued
Namespace Prefix:	dci_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and payable for estimated claims under standard and extended warranty protection rights granted to customers.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.15(5))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 15

-Subparagraph 5

-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph ((c)(5))

-URI http://asc.fasb.org/extlink&oid=6398077&loc=d3e12565-110249

+ Details

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

- Definition

Represents the aggregate decrease in the liability related to payments to satisfy claims for standard and extended product warranties.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph ((c)(2))

-URI http://asc.fasb.org/extlink&oid=6398077&loc=d3e12565-110249

+ Details

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

- Definition

Represents the aggregate Increase or Decrease in the liability during the reporting period for accruals related to preexisting standard and extended product warranties (including adjustments for changes in estimates).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph ((c)(4))

-URI http://asc.fasb.org/extlink&oid=6398077&loc=d3e12565-110249

+ Details

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

- Definition

Represents the aggregate increase in the liability for accruals related to standard and extended product warranties issued during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph ((c)(3))

-URI http://asc.fasb.org/extlink&oid=6398077&loc=d3e12565-110249

+ Details

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

- Details

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Balance Type:	na
Period Type:	duration