Employee Benefit Plans Employee Benefit Plans - Multiemployer Plans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014		Jun. 30, 2014	Dec. 31, 2013		Jun. 30, 2013	Dec. 31, 2012
Multiemployer Plans [Line Items]
Joint Trustee Plan, Percentage By Which Joint Trustee Plan was at Least Funded	80.00%			80.00%			80.00%
Joint Trustee Plan, Period Contributions		$ 9	[1]		$ 9	[1]		$ 12	[1]
UMWA Pension Plan [Member]
Multiemployer Plans [Line Items]
Multiemployer Plans, Withdrawal Obligation, Most Recent Estimate		97
Multiemployer Plans, Certified Zone Status	Red			Orange			Orange
Multiemployer Plan, Period Contributions		$ 2	[1]		$ 3	[1]		$ 3	[1]

[1] PacifiCorp's and Energy West Mining Company's minimum contributions to the plans are based on the amount of wages paid to employees covered by the Local 57 Trust Fund collective bargaining agreements and the number of mining hours worked for the UMWA 1974 Pension Trust, respectively, subject to ERISA minimum funding requirements. As a result of the plan's critical status, Energy West Mining Company was required to begin paying a surcharge for hours worked on and after December 1, 2014.