Fair Value Measurements - MidAmerican Funding - Debt (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, carrying value	$ 37,313	$ 37,972
MidAmerican Funding, LLC and Subsidiaries [Domain]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, carrying value	4,594	4,597
Long-term debt, fair value		5,051
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	42,878	$ 41,785
Level 2 [Member] | MidAmerican Funding, LLC and Subsidiaries [Domain]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	$ 5,280