Fair Value Measurements Debt at at Carrying and Fair Value (Details) (Discounted cash flow [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
PUGET ENERGY [Member] | Carrying Value [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	$ 5,319,933	$ 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	4,690,933	4,662,200
Long Term Debt (variable rate) net of discount	379,000	434,000
PUGET ENERGY [Member] | Fair Value [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	6,266,808	6,896,021
PUGET ENERGY [Member] | Fair Value [Member] | Level 2 [Member]
Liabilities:
Junior subordinated notes	260,160	264,842
Long-term debt (fixed-rate), net of discount	5,627,648	6,197,179
Long Term Debt (variable rate) net of discount	379,000	434,000
Subsidiaries [Member] | Carrying Value [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	3,776,258	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	3,526,258	3,526,258
Subsidiaries [Member] | Fair Value [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	4,374,525	4,893,351
Subsidiaries [Member] | Fair Value [Member] | Level 2 [Member]
Liabilities:
Junior subordinated notes	260,160	264,842
Long-term debt (fixed-rate), net of discount	$ 4,114,365	$ 4,628,509