Business Acquisitions (Details) (USD $)	12 Months Ended					12 Months Ended			12 Months Ended			12 Months Ended		1 Months Ended										12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 NV Energy Transaction [Member]	Dec. 19, 2013 NV Energy Transaction [Member]	Dec. 31, 2013 Residential real estate brokerage business [Member]	Dec. 31, 2012 Residential real estate brokerage business [Member] OwnedAndOperatedCompanies	Dec. 31, 2012 Residential real estate brokerage franchise business [Member]	Dec. 31, 2013 NV Energy [Member] electricity_customers	Dec. 31, 2012 NV Energy [Member]	Dec. 31, 2011 NV Energy [Member]	Dec. 31, 2013 MEHC [Member] NV Energy Transaction [Member]	Dec. 19, 2013 Common Stock [Member] NV Energy Transaction [Member]	Dec. 31, 2013 Common Stock [Member] NV Energy Transaction [Member]	Dec. 31, 2013 Junior Subordinated Debt [Member] NV Energy Transaction [Member]	Dec. 31, 2013 Cash [Member] NV Energy Transaction [Member]	Dec. 31, 2013 Subsidiary Debt [Member]	Dec. 31, 2013 Subsidiary Debt [Member] NV Energy [Member]	Dec. 31, 2013 MEHC [Member] Senior Notes [Member]	Nov. 08, 2013 MEHC [Member] Senior Notes [Member]	Dec. 31, 2013 NV Energy [Member] Subsidiary Debt [Member]	Dec. 31, 2013 NV Energy [Member] Subsidiary Debt [Member] Senior Notes, 6.250%, due 2020 [Member]	Dec. 31, 2012 NV Energy [Member] Subsidiary Debt [Member] Senior Notes, 6.250%, due 2020 [Member]	Dec. 31, 2013 Change in Control Costs [Member] NV Energy Transaction [Member]	Dec. 31, 2013 Donations [Member] NV Energy Transaction [Member]	Dec. 31, 2012 Noncontrolling interest put option [Member] Residential real estate brokerage franchise business [Member]	Dec. 31, 2012 Noncontrolling interest call option [Member] Residential real estate brokerage franchise business [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired	$ 5,536,000,000	$ 591,000,000	$ 0			$ 240,000,000
Business Acquisition, Share Price													$ 23.75
Business Acquisition, Percentage of Voting Interests Acquired								66.70%					100.00%
Number of electricity customers									1,200,000
Number of natural gas customers									200,000
Credit to retail customers				20,000,000
Number of days for retail customers bill credit				30 days
Return on common equity percentage				10.00%
Recovery of loss on revenues				50.00%
Costs and expenses of an acquired entity				38,000,000																				22,000,000	16,000,000
Cash and equivalents assumed					304,000,000
Current assets, including cash and cash equivalents					1,157,000,000
Property, plant, and equipment assumed					9,623,000,000
Goodwill	7,527,000,000	5,120,000,000	4,996,000,000		2,280,000,000				2,280,000,000	0	0
Other long-term assets assumed					1,212,000,000
Total assets assumed					14,272,000,000
Current liabilities, including current portion of long-term debt assumed					872,000,000
Current portion of long-term debt assumed					211,000,000
Subsidiary debt, less current portion assumed		590,000,000			5,085,000,000
Deferred income taxes assumed					1,723,000,000
Other long-term liabilities assumed					996,000,000
Other long-term liabilities assumed					8,676,000,000
Net assets acquired					5,596,000,000
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value		65,000,000
Business Combination, Acquisition Related Costs												5,000,000
Purchase price allocation period	12 months
Goodwill, acquired during period	2,472,000,000	112,000,000				188,000,000			2,280,000,000	0
Payments to Acquire Intangible Assets		92,000,000
Number of Businesses Acquired							5
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners																										33.30%	33.30%
Stated interest rate																						6.25%	0.00%
Payments to Acquire Businesses, Gross														1,000,000,000	2,600,000,000	2,000,000,000
Par value	31,956,000,000																22,737,000,000	5,242,000,000	6,625,000,000	2,000,000,000	510,000,000	315,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities						$ 271,000,000