Commitments and Contingencies Environmental (Details) $ in Millions	Jun. 30, 2019 USD ($)
Environmental remediation obligations [Member]
Environmental remediation obligation, minimum	$ 26.6
Environmental remediation obligation, maximum	34.6
Accrual for environmental loss contingencies	29.0
Combined Manufacturing Sites [Member] \| Manufactured Gas Plants [Member]
Accrual for environmental loss contingencies	22.1
Aberdeen South Dakota Site [Member] \| Manufactured Gas Plants [Member]
Accrual for environmental loss contingencies	8.0
Environmental remediation obligation through 2023	$ 3.4

Total costs accrued as of the balance sheet date for environmental loss contingencies.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942415&loc=d3e14326-108349

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 25
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859

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