New Accounting Pronouncements Revenue Recognition (Details)	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Contracts with Customers from Rate-Regulated Sales of Electricity and Natural Gas Dur	86.90%	91.40%

Contracts with Customers from Rate-Regulated Sales of Electricity and Natural Gas Dur

No definition available.

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Namespace Prefix:	psd_
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Balance Type:	na
Period Type:	duration