Fair Value Measurements Assets and Liabilities Measured on Recurring Basis (Details) (Fair Value, Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
PUGET ENERGY [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	$ 0		$ 0
Derivative Liabilities	0		0
PUGET ENERGY [Member] | Level 1 [Member] | Commodity Contract [Member] | Electric derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0		0
Derivative Liabilities	0		0
PUGET ENERGY [Member] | Level 1 [Member] | Commodity Contract [Member] | Natural gas derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0		0
Derivative Liabilities	0		0
PUGET ENERGY [Member] | Level 1 [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	0		0
PUGET ENERGY [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	7,491		2,340
Derivative Liabilities	291,720		413,904
PUGET ENERGY [Member] | Level 2 [Member] | Commodity Contract [Member] | Electric derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	4,116		2,340
Derivative Liabilities	120,190		165,643
PUGET ENERGY [Member] | Level 2 [Member] | Commodity Contract [Member] | Natural gas derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	3,375		0
Derivative Liabilities	151,383		195,852
PUGET ENERGY [Member] | Level 2 [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	20,147		52,409
PUGET ENERGY [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	15,463		14,391
Derivative Liabilities	98,735		109,743
PUGET ENERGY [Member] | Level 3 [Member] | Commodity Contract [Member] | Electric derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	9,438	[1]	8,380
Derivative Liabilities	89,891	[1]	98,691
PUGET ENERGY [Member] | Level 3 [Member] | Commodity Contract [Member] | Natural gas derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	6,025	[1]	6,011
Derivative Liabilities	8,844	[1]	11,052
PUGET ENERGY [Member] | Level 3 [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	0		0
PUGET ENERGY [Member] | Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	22,954		16,731
Derivative Liabilities	390,455		523,647
PUGET ENERGY [Member] | Total [Member] | Commodity Contract [Member] | Electric derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	13,554		10,720
Derivative Liabilities	210,081		264,334
PUGET ENERGY [Member] | Total [Member] | Commodity Contract [Member] | Natural gas derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	9,400		6,011
Derivative Liabilities	160,227		206,904
PUGET ENERGY [Member] | Total [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	20,147		52,409
PUGET SOUND ENERGY, INC. [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0		0
Derivative Liabilities	0		0
PUGET SOUND ENERGY, INC. [Member] | Level 1 [Member] | Commodity Contract [Member] | Electric derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0		0
Derivative Liabilities	0		0
PUGET SOUND ENERGY, INC. [Member] | Level 1 [Member] | Commodity Contract [Member] | Natural gas derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0		0
Derivative Liabilities	0		0
PUGET SOUND ENERGY, INC. [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	7,491		2,340
Derivative Liabilities	271,573		361,495
PUGET SOUND ENERGY, INC. [Member] | Level 2 [Member] | Commodity Contract [Member] | Electric derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	4,116		2,340
Derivative Liabilities	120,190		165,643
PUGET SOUND ENERGY, INC. [Member] | Level 2 [Member] | Commodity Contract [Member] | Natural gas derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	3,375		0
Derivative Liabilities	151,383		195,852
PUGET SOUND ENERGY, INC. [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	15,463		14,391
Derivative Liabilities	98,735		109,743
PUGET SOUND ENERGY, INC. [Member] | Level 3 [Member] | Commodity Contract [Member] | Electric derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	9,438		8,380
Derivative Liabilities	89,891		98,691
PUGET SOUND ENERGY, INC. [Member] | Level 3 [Member] | Commodity Contract [Member] | Natural gas derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	6,025		6,011
Derivative Liabilities	8,844		11,052
PUGET SOUND ENERGY, INC. [Member] | Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	22,954		16,731
Derivative Liabilities	370,308		471,238
PUGET SOUND ENERGY, INC. [Member] | Total [Member] | Commodity Contract [Member] | Electric derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	13,554		10,720
Derivative Liabilities	210,081		264,334
PUGET SOUND ENERGY, INC. [Member] | Total [Member] | Commodity Contract [Member] | Natural gas derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	9,400		6,011
Derivative Liabilities	$ 160,227		$ 206,904

[1] The valuation techniques, unobservable inputs and ranges are the same for asset and liability positions.