Accounting for Derivative Instruments and Hedging Activities Net Amount of Derivatives Reported in the Statement of Financial Position (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Commodity Contract [Member]
Assets
Gross Amount Recognized in the Statement of Financial Position	$ 34,862	[1]	$ 21,683	[1]
Gross Amounts Offset in the Statement of Financial Position	0		0
Net of Amounts Presented in the Statement of Financial Position	34,862		21,683
Commodity Contracts	(26,785)		(14,126)
Cash Collateral Received	0		0
Net Amount	8,077		7,557
Liabilities
Gross Amount Recognized in the Statement of Financial Position	113,219	[1]	239,271	[1]
Gross Amounts Offset in the Statement of Financial Position	0		0
Net of Amounts Presented in the Statement of Financial Position	113,219		239,271
Commodity Contracts	(26,785)		(14,126)
Cash Collateral Posted	0		0
Net Amount	86,434		225,145
Interest Rate Contract [Member]
Liabilities
Gross Amount Recognized in the Statement of Financial Position	19,966	[1],[2]	21,524	[1],[2]
Gross Amounts Offset in the Statement of Financial Position	0	[2]	0	[2]
Net of Amounts Presented in the Statement of Financial Position	19,966	[2]	21,524	[2]
Commodity Contracts	0	[2]	0	[2]
Cash Collateral Posted	0	[2]	0	[2]
Net Amount	$ 19,966	[2]	$ 21,524	[2]

[1] All Derivative Contract deals are executed under ISDA, NAESB and WSPP Master Netting Agreements with Right of Offset.

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