Recent Financing Transactions - Credit Facilities (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended
	Jun. 30, 2012 Senior unsecured credit facility, $600 million, expiring June 2017 [Member] MEHC [Member] Line of Credit [Member]	Jun. 30, 2012 Unsecured credit facility, $635 million, expiring October 2012 [Member] PacifiCorp [Member] Line of Credit [Member]	Jun. 30, 2012 Unsecured credit facility, $600 million, expiring June 2017 [Member] PacifiCorp [Member] Line of Credit [Member]	Jun. 30, 2012 Letter of credit and reimbursement facility, Topaz [Member] Topaz [Member] Letter of Credit [Member]	Feb. 29, 2012 Letter of credit and reimbursement facility, Topaz [Member] Topaz [Member] Letter of Credit [Member]	Jun. 30, 2012 Equity funding and contribution agreement [Member] MEHC [Member]	Jun. 30, 2012 Letter of credit facility, Agua Caliente [Member] MEHC [Member] Letter of Credit [Member]	Jan. 31, 2012 Letter of credit facility, Agua Caliente [Member] MEHC [Member] Letter of Credit [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 600	$ 635	$ 600		$ 345			$ 303
Line of Credit Facility, Expiration Date	Jun. 30, 2017	Oct. 31, 2012	Jun. 30, 2017
Line of Credit Facility, Amount Outstanding	0		0	42			207
Debt to capitalization ratio	0.70		0.65
Equity funding and contribution agreement, amount committed						$ 303