Fair Value Measurements Debt at at Carrying and Fair Value (Details) (Discounted cash flow [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
PUGET ENERGY [Member] | Carrying Value [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	$ 5,239,693	$ 5,346,200
PUGET ENERGY [Member] | Carrying Value [Member] | Level 2 [Member]
Liabilities:
Junior subordinated notes	250,000	250,000
Long-term debt (fixed-rate), net of discount	4,690,693	4,662,200
Long Term Debt (variable rate) net of discount	299,000	434,000
PUGET ENERGY [Member] | Fair Value [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	6,222,689	6,896,021
PUGET ENERGY [Member] | Fair Value [Member] | Level 2 [Member]
Liabilities:
Junior subordinated notes	258,389	264,842
Long-term debt (fixed-rate), net of discount	5,665,300	6,197,179
Long Term Debt (variable rate) net of discount	299,000	434,000
Subsidiaries [Member] | Carrying Value [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	3,773,258	3,776,258
Subsidiaries [Member] | Carrying Value [Member] | Level 2 [Member]
Liabilities:
Junior subordinated notes	250,000	250,000
Long-term debt (fixed-rate), net of discount	3,523,258	3,526,258
Subsidiaries [Member] | Fair Value [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	4,402,746	4,893,351
Subsidiaries [Member] | Fair Value [Member] | Level 2 [Member]
Liabilities:
Junior subordinated notes	258,389	264,842
Long-term debt (fixed-rate), net of discount	$ 4,144,357	$ 4,628,509