Retirement Benefits Net Periodic Benefit Cost (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2013 Qualified Pension Benefits [Member]	Dec. 31, 2012 Qualified Pension Benefits [Member]	Sep. 30, 2013 SERP Pension Benefits [Member]	Dec. 31, 2012 SERP Pension Benefits [Member]	Sep. 30, 2013 Other Benefit [Member]	Dec. 31, 2012 Other Benefit [Member]	Sep. 30, 2013 PUGET ENERGY [Member] Qualified Pension Benefits [Member]	Sep. 30, 2012 PUGET ENERGY [Member] Qualified Pension Benefits [Member]	Sep. 30, 2013 PUGET ENERGY [Member] Qualified Pension Benefits [Member]	Sep. 30, 2012 PUGET ENERGY [Member] Qualified Pension Benefits [Member]	Sep. 30, 2013 PUGET ENERGY [Member] SERP Pension Benefits [Member]	Sep. 30, 2012 PUGET ENERGY [Member] SERP Pension Benefits [Member]	Sep. 30, 2013 PUGET ENERGY [Member] SERP Pension Benefits [Member]	Sep. 30, 2012 PUGET ENERGY [Member] SERP Pension Benefits [Member]	Sep. 30, 2013 PUGET ENERGY [Member] Other Benefit [Member]	Sep. 30, 2012 PUGET ENERGY [Member] Other Benefit [Member]	Sep. 30, 2013 PUGET ENERGY [Member] Other Benefit [Member]	Sep. 30, 2012 PUGET ENERGY [Member] Other Benefit [Member]	Sep. 30, 2013 Subsidiaries [Member] Qualified Pension Benefits [Member]	Sep. 30, 2012 Subsidiaries [Member] Qualified Pension Benefits [Member]	Sep. 30, 2013 Subsidiaries [Member] Qualified Pension Benefits [Member]	Sep. 30, 2012 Subsidiaries [Member] Qualified Pension Benefits [Member]	Sep. 30, 2013 Subsidiaries [Member] SERP Pension Benefits [Member]	Sep. 30, 2012 Subsidiaries [Member] SERP Pension Benefits [Member]	Sep. 30, 2013 Subsidiaries [Member] SERP Pension Benefits [Member]	Sep. 30, 2012 Subsidiaries [Member] SERP Pension Benefits [Member]	Sep. 30, 2013 Subsidiaries [Member] Other Benefit [Member]	Sep. 30, 2012 Subsidiaries [Member] Other Benefit [Member]	Sep. 30, 2013 Subsidiaries [Member] Other Benefit [Member]	Sep. 30, 2012 Subsidiaries [Member] Other Benefit [Member]
Components of net periodic benefit cost:
Service cost	$ 14,464	$ 16,926	$ 1,123	$ 1,073	$ 100	$ 139	$ 4,822	$ 4,232	$ 14,464	$ 12,695	$ 375	$ 268	$ 1,123	$ 805	$ 34	$ 35	$ 100	$ 105	$ 4,822	$ 4,232	$ 14,464	$ 12,695	$ 375	$ 268	$ 1,123	$ 805	$ 34	$ 35	$ 100	$ 105
Interest cost	18,565	25,986	1,534	2,152	498	751	6,188	6,496	18,565	19,490	511	538	1,534	1,614	166	188	498	563	6,188	6,496	18,565	19,490	511	538	1,534	1,614	166	188	498	563
Expected return on plan assets							(9,774)	(9,051)	(29,321)	(27,153)	0	0	0	0	(109)	(109)	(327)	(327)	(10,172)	(10,384)	(30,514)	(31,150)	0	0	0	0	(109)	(109)	(327)	(327)
Amortization of prior service cost							(495)	(495)	(1,485)	(1,485)	(4)	0	(13)	0	0	0	0	0	(393)	(393)	(1,180)	(1,180)	(4)	74	(13)	220	7	9	22	27
Amortization of net loss (gain)							722	192	2,167	576	365	176	1,096	527	17	13	52	40	5,153	3,754	15,459	11,261	548	358	1,645	1,074	(71)	(61)	(213)	(184)
Amortization of transition obligation																			0	0	0	0	0	0	0	0	0	12	0	37
Defined Benefit Plan, Net Periodic Benefit Cost							$ 1,463	$ 1,374	$ 4,390	$ 4,123	$ 1,247	$ 982	$ 3,740	$ 2,946	$ 108	$ 127	$ 323	$ 381	$ 5,598	$ 3,705	$ 16,794	$ 11,116	$ 1,430	$ 1,238	$ 4,289	$ 3,713	$ 27	$ 74	$ 80	$ 221