Income Taxes - Components of Income Tax Expense (Benefit) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current:
Federal	$ 4,268	$ 785	$ 42,061
State	0	(50)	385
Deferred:
Federal	100,701	32,706	(38,717)
State	(244)	319	(1,248)
Total income tax expense	104,725	33,760	2,481
PUGET SOUND ENERGY, INC.
Current:
Federal	4,268	653	32,331
State	0	0	385
Deferred:
Federal	145,040	76,369	(31,346)
State	0	1,095	(1,248)
Total income tax expense	$ 149,308	$ 78,117	$ 122