Pension and Other Postretirement Benefits - Schedule of Obligations and Funded Status (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	$ 10,421	$ 11,043
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at beginning of year	14,751
Service cost	194	186	165
Interest cost	602	639	678
Settlements	9		2
Benefit obligation at end of year	13,730	14,751
Funded status	(3,150)	(3,708)
Less: Amounts attributed to joint venture partners	(25)	(40)
Net funded status	(3,125)	(3,668)
Noncurrent assets	88	86
Current liabilities	(30)	(32)
Noncurrent liabilities	(3,183)	(3,722)
Net amount recognized	(3,125)	(3,668)
Net actuarial loss	5,198	5,880
Prior service cost (benefit)	94	119
Total, before tax effect	5,292	5,999
Less: Amounts attributed to joint venture partners	38	54
Net amount recognized, before tax effect	5,254	5,945
Net actuarial (gain) loss	(193)	1,073
Amortization of accumulated net actuarial loss	(489)	(384)	(247)
Prior service cost		9
Amortization of prior service (cost) benefit	(25)	(19)
Total, before tax effect	(707)	679
Less: Amounts attributed to joint venture partners	(16)	8
Net amount recognized, before tax effect	(691)	671
Pension Benefits [Member] | Change in Benefit Obligation [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at beginning of year	14,751	13,526
Service cost	213	203
Interest cost	611	647
Amendments	82	6
Actuarial (gains) losses	(849)	1,120
Settlements	(13)
Benefits paid	(841)	(833)
Foreign currency translation impact	(224)	82
Benefit obligation at end of year	13,730	14,751
Pension Benefits [Member] | Change in Plan Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	11,043	10,311
Actual return on plan assets	109	925
Employer contributions	473	571
Participants' contributions	27	32
Settlements	(17)
Benefits paid	(825)	(822)
Administrative expenses	(40)	(42)
Foreign currency translation impact	(190)	68
Fair value of plan assets at end of year	10,580	11,043
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	17	14	17
Interest cost	114	131	158
Funded status	(2,592)	(2,863)
Less: Amounts attributed to joint venture partners	(4)	(4)
Net funded status	(2,588)	(2,859)
Current liabilities	(234)	(256)
Noncurrent liabilities	(2,354)	(2,603)
Net amount recognized	(2,588)	(2,859)
Net actuarial loss	389	593
Prior service cost (benefit)	(57)	(76)
Total, before tax effect	332	517
Less: Amounts attributed to joint venture partners	(1)	(1)
Net amount recognized, before tax effect	333	518
Net actuarial (gain) loss	(169)	107
Amortization of accumulated net actuarial loss	(35)	(25)	(26)
Amortization of prior service (cost) benefit	19	16
Total, before tax effect	(185)	98
Net amount recognized, before tax effect	(185)	98
Other Postretirement Benefits [Member] | Change in Benefit Obligation [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at beginning of year	2,863	2,844
Service cost	17	14
Interest cost	114	132
Actuarial (gains) losses	(170)	107
Benefits paid	(249)	(256)
Medicare Part D subsidy receipts	20	21
Foreign currency translation impact	(3)	1
Benefit obligation at end of year	2,592	2,863
Other Postretirement Benefits [Member] | Change in Plan Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year		8
Benefits paid		$ (8)