Fair Value Measurements - Assets and Liabilities Measured on Recurring Basis (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Interest Rate Contract
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	$ 9,073	[1]	$ 13,223	[1]
Commodity Contract
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	24,348		26,600
Derivative Liabilities	196,035		72,988
Fair Value, Measurements, Recurring | PUGET ENERGY | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	9,073		13,223
Fair Value, Measurements, Recurring | PUGET ENERGY | Level 2 | Interest Rate Contract
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	9,073		13,223
Fair Value, Measurements, Recurring | PUGET ENERGY | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	0		0
Fair Value, Measurements, Recurring | PUGET ENERGY | Level 3 | Interest Rate Contract
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	0		0
Fair Value, Measurements, Recurring | PUGET ENERGY | Level 3 | Commodity Contract | Electric Portfolio
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	3,168	[2]
Derivative Liabilities	15,230	[2]
Fair Value, Measurements, Recurring | PUGET ENERGY | Level 3 | Commodity Contract | Natural Gas Portfolio
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	1,462	[2]
Derivative Liabilities	3,502	[2]
Fair Value, Measurements, Recurring | PUGET ENERGY | Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	9,073		13,223
Fair Value, Measurements, Recurring | PUGET ENERGY | Total | Interest Rate Contract
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	9,073		13,223
Fair Value, Measurements, Recurring | PUGET SOUND ENERGY, INC. | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	19,718		20,109
Derivative Liabilities	177,303		50,715
Fair Value, Measurements, Recurring | PUGET SOUND ENERGY, INC. | Level 2 | Commodity Contract | Electric Portfolio
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	1,654		14,661
Derivative Liabilities	91,998		18,073
Fair Value, Measurements, Recurring | PUGET SOUND ENERGY, INC. | Level 2 | Commodity Contract | Natural Gas Portfolio
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	18,064		5,448
Derivative Liabilities	85,305		32,642
Fair Value, Measurements, Recurring | PUGET SOUND ENERGY, INC. | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	4,630		6,491
Derivative Liabilities	18,732		22,273
Fair Value, Measurements, Recurring | PUGET SOUND ENERGY, INC. | Level 3 | Commodity Contract | Electric Portfolio
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets			3,818
Derivative Liabilities			19,239
Fair Value, Measurements, Recurring | PUGET SOUND ENERGY, INC. | Level 3 | Commodity Contract | Natural Gas Portfolio
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets			2,673
Derivative Liabilities			3,034
Fair Value, Measurements, Recurring | PUGET SOUND ENERGY, INC. | Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	24,348		26,600
Derivative Liabilities	196,035		72,988
Fair Value, Measurements, Recurring | PUGET SOUND ENERGY, INC. | Total | Commodity Contract | Electric Portfolio
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	4,822		18,479
Derivative Liabilities	107,228		37,312
Fair Value, Measurements, Recurring | PUGET SOUND ENERGY, INC. | Total | Commodity Contract | Natural Gas Portfolio
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	19,526		8,121
Derivative Liabilities	88,807		35,676
Carrying Amount | PUGET ENERGY
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	37,527		44,302
Restricted Cash	32,863		7,171
Notes receivable and other	53,503		53,449
Total assets	123,893		104,922
Short Term Debt	85,000		162,000
Total liabilities	85,000		162,000
Carrying Amount | PUGET ENERGY | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	37,527		44,302
Restricted Cash	32,863		7,171
Notes receivable and other	0		0
Total assets	70,390		51,473
Short Term Debt	85,000		162,000
Total liabilities	85,000		162,000
Carrying Amount | PUGET ENERGY | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	0		0
Restricted Cash	0		0
Notes receivable and other	53,503		53,449
Total assets	53,503		53,449
Short Term Debt	0		0
Total liabilities	0		0
Carrying Amount | PUGET SOUND ENERGY, INC. | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	37,466		44,111
Restricted Cash	32,863		7,171
Notes receivable and other	0		0
Total assets	70,329		51,282
Short Term Debt	85,000		162,000
Short-term debt owed by PSE to Puget Energy	0		0
Total liabilities	85,000		162,000
Carrying Amount | PUGET SOUND ENERGY, INC. | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	0		0
Restricted Cash	0		0
Notes receivable and other	53,503		53,449
Total assets	53,503		53,449
Short Term Debt	0		0
Short-term debt owed by PSE to Puget Energy	28,933		29,598
Total liabilities	28,933		29,598
Carrying Amount | PUGET SOUND ENERGY, INC. | Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	37,466		44,111
Restricted Cash	32,863		7,171
Notes receivable and other	53,503		53,449
Total assets	123,832		104,731
Short Term Debt	85,000		162,000
Short-term debt owed by PSE to Puget Energy	28,933		29,598
Total liabilities	$ 113,933		$ 191,598

[1] Interest Rate Swap Contracts are only held at Puget Energy.

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