Regulation and Rates (Details) (PUGET SOUND ENERGY, INC. [Member], USD $) In Millions, unless otherwise specified	Jun. 28, 2012	May 14, 2012
Regulatory Assets [Line Items]
Rate Case, Approved Effective Weighted Cost of Capital		7.80%
Rate Case, Approved Effective Common Equity in Capital Structure		48.00%
Rate Case, Approved Effective Return on Equity		9.80%
Electric [Member]
Regulatory Assets [Line Items]
Rate Case, Approved Effective Annual Rate Increase		$ 63.3
Rate Case, Approved Effective Annual Rate Percentage Increase		3.20%
Natural Gas [Member]
Regulatory Assets [Line Items]
Rate Case, Approved Effective Annual Rate Increase		13.4
Rate Case, Approved Effective Annual Rate Percentage Increase		1.30%
Accounting Petition, Approved Effective Increase (Decrease) to Revenue	6.9
Accounting Petition, Approved Effective Increase (Decrease) to Conservation Amortization Expense	$ 6.6

Accounting Petition, Approved Effective Increase (Decrease) to Conservation Amortization Expense

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Accounting Petition, Approved Effective Increase (Decrease) to Revenue

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Public Utilities, Rate Case, Approved Effective Annual Rate Increase

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Public Utilities, Rate Case, Approved Effective Annual Rate Percentage Increase

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Public Utilities, Rate Case, Approved Effective Common Equity in Capital Structure

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Public Utilities, Rate Case, Approved Effective Return on Equity

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Public Utilities, Rate Case, Approved Effective Weighted Cost of Capital

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