Pension and Other Postretirement Benefits - Schedule of Obligations and Funded Status (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	$ 11,043	$ 10,339
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at beginning of year	13,526
Service cost	(186)	(165)	(148)
Interest cost	(639)	(678)	(682)
Settlements		(2)	(2)
Curtailments		9	10
Benefit obligation at end of year	14,751	13,526
Funded status	(3,708)	(3,215)
Less: Amounts attributed to joint venture partners	(40)	(34)
Net funded status	(3,668)	(3,181)
Noncurrent assets	86	109
Current liabilities	(32)	(29)
Noncurrent liabilities	(3,722)	(3,261)
Net amount recognized	(3,668)	(3,181)
Net actuarial loss	5,880	5,191
Prior service cost (benefit)	119	129
Total, before tax effect	5,999	5,320
Less: Amounts attributed to joint venture partners	54	46
Net amount recognized, before tax effect	5,945	5,274
Net actuarial loss	1,073	1,216
Amortization of accumulated net actuarial loss	(384)	(246)
Prior service cost (benefit)	9	42
Amortization of prior service (cost) benefit	(19)	(19)
Total, before tax effect	679	993
Less: Amounts attributed to joint venture partners	8	10
Net amount recognized, before tax effect	671	983
Pension Benefits [Member] | Change in Benefit Obligation [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at beginning of year	13,526	12,343
Service cost	203	183
Interest cost	647	687
Amendments	6	40
Actuarial losses	1,120	1,163
Settlements		(32)
Curtailments		(7)
Benefits paid	(833)	(813)
Foreign currency translation impact	82	(38)
Benefit obligation at end of year	14,751	13,526
Pension Benefits [Member] | Change in Plan Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlements		(34)
Benefits paid	(822)	(805)
Foreign currency translation impact	68	(26)
Fair value of plan assets at beginning of year	10,311	9,451
Actual return on plan assets	925	783
Employer contributions	571	945
Participants' contributions	32	35
Administrative expenses	(42)	(38)
Fair value of plan assets at end of year	11,043	10,311
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	(14)	(17)	(20)
Interest cost	(131)	(158)	(174)
Settlements			3
Funded status	(2,863)	(2,836)
Less: Amounts attributed to joint venture partners	(4)	(5)
Net funded status	(2,859)	(2,831)
Current liabilities	(256)	(248)
Noncurrent liabilities	(2,603)	(2,583)
Net amount recognized	(2,859)	(2,831)
Net actuarial loss	593	511
Prior service cost (benefit)	(76)	(92)
Total, before tax effect	517	419
Less: Amounts attributed to joint venture partners	(1)	(1)
Net amount recognized, before tax effect	518	420
Net actuarial loss	107	17
Amortization of accumulated net actuarial loss	(25)	(26)
Prior service cost (benefit)		(1)
Amortization of prior service (cost) benefit	16	17
Total, before tax effect	98	7
Less: Amounts attributed to joint venture partners		(1)
Net amount recognized, before tax effect	98	8
Other Postretirement Benefits [Member] | Change in Benefit Obligation [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at beginning of year	2,844	2,902
Service cost	14	17
Interest cost	132	159
Amendments		(1)
Actuarial losses	107	17
Benefits paid	(256)	(275)
Medicare Part D subsidy receipts	21	25
Foreign currency translation impact	1
Benefit obligation at end of year	2,863	2,844
Other Postretirement Benefits [Member] | Change in Plan Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefits paid	(8)	(52)
Fair value of plan assets at beginning of year	8	58
Actual return on plan assets		2
Fair value of plan assets at end of year		$ 8