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	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Commodity Contract [Member]		Dec. 31, 2012 Commodity Contract [Member]		Jun. 30, 2013 Interest Rate Contract [Member]		Dec. 31, 2012 Interest Rate Contract [Member]
Derivative [Line Items]
Derivative contracts classified as financing activities due to merger	$ (26,013)	$ (47,423)
Assets
Gross Amount Recognized in the Statement of Financial Position			16,891	[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			16,891		21,683
Commodity Contracts			(10,434)		(14,126)
Cash Collateral Received			0		0
Net Amount			6,457		7,557
Liabilities
Gross Amount Recognized in the Statement of Financial Position			160,725	[1]	239,271	[1]	13,706	[1],[2]	21,524	[1],[2]
Gross Amounts Offset in the Statement of Financial Position			0		0		0	[2]	0	[2]
Net of Amounts Presented in the Statement of Financial Position			160,725		239,271		13,706	[2]	21,524	[2]
Commodity Contracts			(10,434)		(14,126)		0	[2]	0	[2]
Cash Collateral Posted			0		0		0	[2]	0	[2]
Net Amount			$ 150,291		$ 225,145		$ 13,706	[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.