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Regulated Operations (Details)	Nov. 15, 2022 $ / dekatherm
Regulated Operations [Abstract]
Demand Rate	0.37250
Commodity Rate	0.00935

The commodity rate approved by the Federal Energy Regulatory Commission (FERC).

No definition available.

Name:	nwp_CommodityRate
Namespace Prefix:	nwp_
Data Type:	srt-types:perUnitItemType
Balance Type:	na
Period Type:	instant

The demand rate approved by the Federal Energy Regulatory Commisssion (FERC).

No definition available.

Name:	nwp_DemandRate
Namespace Prefix:	nwp_
Data Type:	srt-types:perUnitItemType
Balance Type:	na
Period Type:	instant

No definition available.

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Period Type:	duration