Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

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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

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ References

+ Details

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Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- 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

The carrying value as of the balance sheet date of the noncurrent portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 45
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=99376301&loc=d3e1314-112600

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 45
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=99376301&loc=d3e1336-112600

+ Details

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

- Details

Name:	us-gaap_CreditFacilityAxis=wso_SwinglineSubfacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=wso_MulticurrencyBorrowingSublimitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember
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Data Type:	na
Balance Type:
Period Type:

- Details

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Balance Type:
Period Type:

- Details

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- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
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Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
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- Details

Name:	us-gaap_VariableRateAxis=us-gaap_PrimeRateMember
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Debt - Additional Information (Detail) - USD ($)	12 Months Ended
Debt - Additional Information (Detail) - USD ($)	Dec. 31, 2017	Feb. 05, 2018	Dec. 31, 2016
Debt Instrument [Line Items]
Revolving credit agreement maturity date	Jul. 01, 2019
Revolving credit agreement maximum borrowing capacity	$ 600,000,000
Commitment fee percentage on unused portion of the commitment	0.125%
Borrowings under revolving credit agreement	$ 21,800,000		$ 235,294,000
Swingline Subfacility
Debt Instrument [Line Items]
Revolving credit agreement maximum borrowing capacity	90,000,000
Multicurrency Borrowing Sublimit
Debt Instrument [Line Items]
Revolving credit agreement maximum borrowing capacity	75,000,000
Letter of Credit
Debt Instrument [Line Items]
Revolving credit agreement maximum borrowing capacity	$ 10,000,000
Subsequent Event
Debt Instrument [Line Items]
Revolving credit agreement maximum borrowing capacity		$ 300,000,000
Minimum
Debt Instrument [Line Items]
Commitment fee percentage on unused portion of the commitment	0.125%
Maximum
Debt Instrument [Line Items]
Commitment fee percentage on unused portion of the commitment	0.35%
London Interbank Offer Rate
Debt Instrument [Line Items]
Basis spread	0.875%
London Interbank Offer Rate \| Minimum
Debt Instrument [Line Items]
Basis spread	0.875%
London Interbank Offer Rate \| Maximum
Debt Instrument [Line Items]
Basis spread	2.50%
Prime Rate
Debt Instrument [Line Items]
Basis spread	0.00%
Prime Rate \| Minimum
Debt Instrument [Line Items]
Basis spread	0.00%
Prime Rate \| Maximum
Debt Instrument [Line Items]
Basis spread	1.50%