Fair Value Measurements Debt at at Carrying and Fair Value (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2011
PUGET ENERGY [Member] | Carrying Amount [Member] | Level 2 [Member]
Liabilities:
Long Term Debt (variable-rate), net of discount	$ 0
Discounted cash flow [Member] | PUGET ENERGY [Member] | Carrying Amount [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	5,320,278	5,346,200
Discounted cash flow [Member] | PUGET ENERGY [Member] | Carrying Amount [Member] | Level 2 [Member]
Liabilities:
Junior subordinated notes	250,000	250,000
Long-term debt (fixed-rate), net of discount	4,665,278	4,662,200
Long Term Debt (variable-rate), net of discount	405,000	434,000
Discounted cash flow [Member] | PUGET ENERGY [Member] | Fair Value [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	6,789,006	6,896,021
Discounted cash flow [Member] | PUGET ENERGY [Member] | Fair Value [Member] | Level 2 [Member]
Liabilities:
Junior subordinated notes	266,968	264,842
Long-term debt (fixed-rate), net of discount	6,117,038	6,197,179
Long Term Debt (variable-rate), net of discount	405,000	434,000
Discounted cash flow [Member] | PUGET SOUND ENERGY, INC. [Member] | Carrying Amount [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	3,776,258	3,776,258
Discounted cash flow [Member] | PUGET SOUND ENERGY, INC. [Member] | Carrying Amount [Member] | Level 2 [Member]
Liabilities:
Junior subordinated notes	250,000	250,000
Long-term debt (fixed-rate), net of discount	3,526,258	3,526,258
Discounted cash flow [Member] | PUGET SOUND ENERGY, INC. [Member] | Fair Value [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	4,789,494	4,893,351
Discounted cash flow [Member] | PUGET SOUND ENERGY, INC. [Member] | Fair Value [Member] | Level 2 [Member]
Liabilities:
Junior subordinated notes	266,968	264,842
Long-term debt (fixed-rate), net of discount	$ 4,522,526	$ 4,628,509