For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9054-108599

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6351-108592

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13531-108611

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
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Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Risks, Uncertainties, Contingencies and Litigation (Details) $ in Millions	12 Months Ended
	Mar. 31, 2021 USD ($) Customer	Mar. 31, 2020 USD ($) Customer	Mar. 31, 2019 Customer
Environmental loss contingencies [Abstract]
Reserves for environmental matters \| $	$ 16.0	$ 18.2
Sales [Member] \| Customer Concentration Risk [Member] \| Top Ten Customers [Member]
Credit Risk [Abstract]
Concentration risk, percentage	43.00%	45.00%	50.00%
Accounts Receivable [Member] \| Credit Concentration Risk [Member]
Credit Risk [Abstract]
Number of top customers	10
Accounts Receivable [Member] \| Credit Concentration Risk [Member] \| Top Ten Customers [Member]
Credit Risk [Abstract]
Concentration risk, percentage	35.00%	34.00%
Vehicular [Member]
Credit Risk [Abstract]
Number of major customers	1	1	2