Business Acquisitions (Details)	3 Months Ended
	Mar. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 19, 2013 NV Energy Transaction [Member] USD ($)	Dec. 31, 2013 NV Energy, Inc. [Member] electricity_customers natural_gas_customers	Mar. 31, 2014 Senior notes, 6.250%, due 2020 [Member] NVE Holdings [Member] NV Energy, Inc. [Member] Subsidiary Debt [Member]	May 01, 2014 Subsequent Event [Member] AltaLink, LP [Member] USD ($)	May 01, 2014 Subsequent Event [Member] AltaLink, LP [Member] CAD
Business Acquisition [Line Items]
Number of electricity customers				1,200,000
Number of natural gas customers				200,000
Business acquisition, measurement period	12 months
Debt instrument, interest rate, stated percentage					6.25%
Cash and cash equivalents assumed			$ 304,000,000
Current assets, including cash and cash equivalents			1,160,000,000
Property, plant, and equipment			9,550,000,000
Goodwill	7,609,000,000	7,527,000,000	2,362,000,000
Other long-term assets			1,321,000,000
Total assets			14,393,000,000
Current portion of long-term debt assumed			218,000,000
Current liabilities, including current portion of long-term debt			882,000,000
Subsidiary debt, less current portion			5,124,000,000
Deferred income taxes			1,757,000,000
Other long-term liabilities			1,034,000,000
Total liabilities			8,797,000,000
Net assets acquired			5,596,000,000
Business acquisition expected cash payment						$ 2,900,000,000	3,200,000,000