Retirement Benefits (Tables)

3 Months Ended

Mar. 31, 2013

Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]

Schedule of Changes in Projected Benefit Obligations

The following table summarizes the Company’s change in benefit obligation for the periods ended March 31, 2013 and December 31, 2012:

Puget Energy and Puget Sound Energy	Qualified Pension Benefits						SERP Pension Benefits						Other Benefits
	Three Months Ended			Year Ended			Three Months Ended			Year Ended			Three Months Ended			Year Ended
(Dollars in Thousands)	March 31, 2013			December 31, 2012			March 31, 2013			December 31, 2012			March 31, 2013			December 31, 2012
Change in benefit obligation:
Benefit obligation at beginning of period	$	616,290		$	565,997		$	51,795		$	48,370		$	17,672		$	16,436
Service cost	4,709			16,926			375			1,073			34			139
Interest cost	6,194			25,986			511			2,152			177			751
Amendment	—			—			—			(122		)	—			—
Actuarial loss/(gain)	—			40,914			—			5,483			—			1,199
Benefits paid	(9,625		)	(33,533		)	(444		)	(5,161		)	(420		)	(1,523		)
Medicare part D subsidiary received	—			—			—			—			—			670
Benefit obligation at end of period	$	617,568		$	616,290		$	52,237		$	51,795		$	17,463		$	17,672

PUGET ENERGY [Member]

Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]

Schedule of Net Benefit Costs

following tables summarize the Company’s net periodic benefit cost for the three months ended March 31, 2013 and 2012:

Puget Energy
Three Months Ended March 31,	Qualified Pension Benefits						SERP Pension Benefits					Other Benefits
(Dollars in Thousands)	2013			2012			2013			2012		2013			2012
Components of net periodic benefit cost:
Service cost	$	4,709		$	4,235		$	375		$	268	$	34		$	38
Interest cost	6,194			6,442			511			538		176			187
Expected return on plan assets	(9,851		)	(9,001		)	—			—		(108		)	(108		)
Amortization of prior service cost	(495		)	(495		)	(4		)	—		—			—
Amortization of net loss (gain)	650			149			365			176		17			9
Net periodic benefit cost	$	1,207		$	1,330		$	1,247		$	982	$	119		$	126

PUGET SOUND ENERGY, INC. [Member]

Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]

Schedule of Net Benefit Costs

Puget Sound Energy
Three Months Ended March 31,	Qualified Pension Benefits						SERP Pension Benefits					Other Benefits
(Dollars in Thousands)	2013			2012			2013			2012		2013			2012
Components of net periodic benefit cost:
Service cost	$	4,709		$	4,235		$	375		$	268	$	34		$	38
Interest cost	6,194			6,442			511			538		176			187
Expected return on plan assets	(10,249		)	(10,333		)	—			—		(108		)	(108		)
Amortization of prior service cost	(393		)	(393		)	(4		)	73		8			9
Amortization of net loss (gain)	5,085			3,717			548			358		(34		)	(60		)
Amortization of transition obligation	—			—			—			—		—			12
Net periodic benefit cost	$	5,346		$	3,668		$	1,430		$	1,237	$	76		$	78