Long-Term Debt - Additional Information (Detail)	3 Months Ended
Mar. 31, 2018 USD ($) lender
Debt Instrument [Line Items]
Multi-currency revolving credit agreement	$ 500,000,000
Number of banks involved in multi-year multi-currency revolving credit agreement \| lender	9
Revolving credit facility, expiration date	Dec. 15, 2021
Multi-currency revolving credit agreement, maximum amount	$ 700,000,000

Number Of Banks Involved In Multi-Year Multi-Currency Revolving Credit Agreement

No definition available.

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Namespace Prefix:	aos_
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- 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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- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ 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 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

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

+ References

+ Details

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Data Type:	xbrli:dateItemType
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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

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant