XML 91 R76.htm IDEA: XBRL DOCUMENT v3.8.0.1

Weighted Asset Allocations by Asset Category (Detail)	Dec. 31, 2017	Dec. 31, 2016
Pension And Other Post-Retirement Benefits
Average Assets Allocation	100.00%	100.00%
Equity Securities
Pension And Other Post-Retirement Benefits
Average Assets Allocation	45.00%	48.00%
Debt Securities
Pension And Other Post-Retirement Benefits
Average Assets Allocation	43.00%	37.00%
Real estate
Pension And Other Post-Retirement Benefits
Average Assets Allocation	9.00%	10.00%
Private equity
Pension And Other Post-Retirement Benefits
Average Assets Allocation	2.00%	4.00%
Other
Pension And Other Post-Retirement Benefits
Average Assets Allocation	1.00%	1.00%

X

- References

No definition available.

+ Details

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

X

- Definition

Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2446-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_RealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=aos_PrivateEquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=aos_AllOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: