Commitments and Contingent Liabilities (Schedule of Purchased Water Costs) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Purchased Water
Untreated	$ 3.4	$ 3.4	$ 3.6
Treated	3.6	3.2	3.2
Total Costs	$ 7.0	$ 6.6	$ 6.8

Cost of water purchased, may include any water related assessment. If water is bought on a unit volume basis, would also be considered as commodity costs.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2)
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration