Accounting for Derivative Instruments and Hedging Activities Net Amount of Derivatives Reported in the Statement of Financial Position (Details) $ in Thousands, MMBTU in Millions		Mar. 31, 2017 USD ($) MMBTU	Dec. 31, 2016 USD ($) MMBTU
Liabilities:
Derivative Asset, Current		$ 23,501	$ 54,341
Derivative Liability, Current		41,623	44,310
Derivative Asset, Noncurrent		5,546	8,738
Derivative Liability, Noncurrent		23,155	16,261
Commodity Contract [Member]
Assets:
Gross Amount Recognized in the Statement of Financial Position	[1]	29,047	63,079
Gross Amounts Offset in the Statement of Financial Position		0	0
Net of Amounts Presented in the Statement of Financial Position		29,047	63,079
Commodity Contracts		(21,525)	(42,858)
Cash Collateral Received		0	0
Net Amount		7,522	20,221
Liabilities:
Gross Amount Recognized in the Statement of Financial Position	[1]	64,778	60,430
Gross Amounts Offset in the Statement of Financial Position		0	0
Net of Amounts Presented in the Statement of Financial Position		64,778	60,430
Commodity Contracts		(21,525)	(42,858)
Cash Collateral Posted		0	0
Net Amount		43,253	17,572
Interest Rate Contract [Member]
Liabilities:
Gross Amount Recognized in the Statement of Financial Position	[1],[2]		141
Gross Amounts Offset in the Statement of Financial Position	[2]		0
Net of Amounts Presented in the Statement of Financial Position			141
Commodity Contracts	[2]		0
Cash Collateral Posted	[2]		0
Net Amount			141
Subsidiaries [Member]
Liabilities:
Derivative Asset, Current		23,501	54,341
Derivative Liability, Current		41,623	44,170
Derivative Asset, Noncurrent		5,546	8,738
Derivative Liability, Noncurrent		23,155	16,261
Not Designated as Hedging Instrument [Member]
Assets:
Net of Amounts Presented in the Statement of Financial Position		29,047	63,079
Liabilities:
Net of Amounts Presented in the Statement of Financial Position		64,778	60,571
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount		0	450,000
Assets:
Net of Amounts Presented in the Statement of Financial Position		0	0
Liabilities:
Net of Amounts Presented in the Statement of Financial Position		0	141
Not Designated as Hedging Instrument [Member] | Electric Portfolio [Member]
Assets:
Net of Amounts Presented in the Statement of Financial Position		20,343	36,460
Liabilities:
Net of Amounts Presented in the Statement of Financial Position		$ 44,499	$ 41,329
Not Designated as Hedging Instrument [Member] | Natural Gas Derivatives [Member]
Liabilities:
Derivative, Nonmonetary Notional Amount | MMBTU		304.7	336.4
Not Designated as Hedging Instrument [Member] | Natural Gas Portfolio [Member]
Assets:
Net of Amounts Presented in the Statement of Financial Position		$ 8,704	$ 26,619
Liabilities:
Net of Amounts Presented in the Statement of Financial Position		20,279	19,101
Not Designated as Hedging Instrument [Member] | Parent Company [Member]
Liabilities:
Derivative Asset, Current		23,501	54,341
Derivative Liability, Current		41,623	44,310
Derivative Asset, Noncurrent		5,546	8,738
Derivative Liability, Noncurrent		$ 23,155	$ 16,261

[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.