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Earnings Per Share (Narrative) (Details) (Class B Common Stock [Member])	Sep. 30, 2011	Sep. 30, 2010
Class B Common Stock [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Conversion of stock into common stock, shares convertible	2,853,096	2,858,592

X

- 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.

+ Details

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Namespace Prefix:	us-gaap
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Balance Type:	na
Period Type:	duration

X

- Definition

Convertible Class B common stock outstanding.

+ Details

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Namespace Prefix:	wso
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant