Accounting for Derivative Instruments and Hedging Activities Net Amount of Derivatives Reported in the Statement of Financial Position (Details) - Entity [Domain] - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Liabilities
Derivative contracts classified as financing activities due to merger		$ (8,045)	$ (8,026)
Commodity Contract [Member]
Assets
Gross Amount Recognized in the Statement of Financial Position	[1]	21,088		$ 24,348
Gross Amounts Offset in the Statement of Financial Position		0		0
Net of Amounts Presented in the Statement of Financial Position		21,088		24,348
Commodity Contracts		(16,491)		(23,066)
Cash Collateral Received		0		0
Net Amount		4,597		1,282
Liabilities
Gross Amount Recognized in the Statement of Financial Position	[1]	167,748		196,035
Gross Amounts Offset in the Statement of Financial Position		0		0
Net of Amounts Presented in the Statement of Financial Position		167,748		196,035
Commodity Contracts		(16,491)		(23,066)
Cash Collateral Posted		0		(20)
Net Amount		151,257		172,949
Interest Rate Contract [Member]
Liabilities
Gross Amount Recognized in the Statement of Financial Position	[1],[2]	8,294		9,073
Gross Amounts Offset in the Statement of Financial Position	[2]	0		0
Net of Amounts Presented in the Statement of Financial Position	[2]	8,294		9,073
Commodity Contracts	[2]	0		0
Cash Collateral Posted	[2]	0		0
Net Amount	[2]	$ 8,294		$ 9,073

[1] 1 All derivative contract deals are executed under ISDA, NAESB and WSPP master netting agreements with right of set-off.

[2] 2 Interest rate swap contracts are only held at Puget Energy.