Fair Value Measurements Debt at at Carrying and Fair Value (Details) (Discounted cash flow [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
PUGET ENERGY [Member] | Carrying Amount [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	$ 5,337,633	$ 5,277,367
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	4,653,633	4,197,511
Long Term Debt (variable-rate), net of discount	434,000	829,856
PUGET ENERGY [Member] | Fair Value [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	6,764,292	6,609,132
PUGET ENERGY [Member] | Fair Value [Member] | Level 2 [Member]
Liabilities:
Junior subordinated notes	252,313	248,583
Long-term debt (fixed-rate), net of discount	6,077,979	5,503,571
Long Term Debt (variable-rate), net of discount	434,000	856,978
PUGET SOUND ENERGY, INC. [Member] | Carrying Amount [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	3,773,846	3,773,845
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	3,523,846	3,523,845
PUGET SOUND ENERGY, INC. [Member] | Fair Value [Member]
Liabilities:
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	4,858,533	4,747,878
PUGET SOUND ENERGY, INC. [Member] | Fair Value [Member] | Level 2 [Member]
Liabilities:
Junior subordinated notes	252,313	248,583
Long-term debt (fixed-rate), net of discount	$ 4,606,220	$ 4,499,295