Components of Accumulated Other Comprehensive Loss, Net (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, December 31, 2012 - accumulated other comprehensive loss attributable to MEHC shareholders, net			$ (463)
Other comprehensive income (loss), unrecognized amounts on retirement benefits	10	16	57	11
Other comprehensive income (loss), foreign currency translation adjustment	(1)	(56)	(213)	29
Other comprehensive income (loss), unrealized gains on available-for-sale securities	17	(124)	44	(35)
Other comprehensive income (loss), unrealized gains on cash flow hedges	(9)	12	7	(3)
Other comprehensive income (loss)	17	(152)	(105)	2
Balance, June 30, 2013 - accumulated other comprehensive loss attributable to MEHC shareholders, net	(568)		(568)
Accumulated Other Comprehensive Loss, Net [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, December 31, 2012 - unrecognized amounts on retirement benefits			(575)
Balance, December 31, 2012 - foreign currency translation adjustment			(172)
Balance, December 31, 2012 - unrealized gains on available-for-sale securities			261
Balance, December 31, 2012 - unrealized gains on cash flow hedges			23
Balance, December 31, 2012 - accumulated other comprehensive loss attributable to MEHC shareholders, net			(463)
Other comprehensive income (loss), unrecognized amounts on retirement benefits			57
Other comprehensive income (loss), foreign currency translation adjustment			(213)
Other comprehensive income (loss), unrealized gains on available-for-sale securities			44
Other comprehensive income (loss), unrealized gains on cash flow hedges			7
Other comprehensive income (loss)			(105)	2
Balance, June 30, 2013 - unrecognized amounts on retirement benefits	(518)		(518)
Balance, June 30, 2013 - foreign currency translation adjustment	(385)		(385)
Balance, June 30, 2013 - unrealized gains on available-for-sale securities	305		305
Balance, June 30, 2013 - unrealized gains on cash flow hedges	30		30
Balance, June 30, 2013 - accumulated other comprehensive loss attributable to MEHC shareholders, net	$ (568)		$ (568)