Pension Plans, Other Postretirement Benefits, and Defined-Contribution Plans - Changes in the Fair Value of Level 3 Assets Table (Detail) (Investments [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Actual return on plan assets
Fair value of plan assets at end of year	$ 1,769	[1]	$ 1,469	[1]
Hedge Funds and Other Alternative Strategies Asset Position [Member]
Actual return on plan assets
Fair value of plan assets at end of year	110		97
Private Equity [Member]
Actual return on plan assets
Fair value of plan assets at end of year	72		64
Real Estate [Member]
Actual return on plan assets
Fair value of plan assets at end of year	133		124
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	219	[1]	191
Acquisitions (dispositions), net	(4)		15
Actual return on plan assets
Relating to assets sold during the reporting period	5		0
Relating to assets still held at the reporting date	17		13
Fair value of plan assets at end of year	237	[1]	219	[1]
Fair Value, Inputs, Level 3 [Member] | Hedge Funds and Other Alternative Strategies Asset Position [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	77		64
Acquisitions (dispositions), net	(6)		9
Actual return on plan assets
Relating to assets sold during the reporting period	1		(2)
Relating to assets still held at the reporting date	7		6
Fair value of plan assets at end of year	79		77
Fair Value, Inputs, Level 3 [Member] | Private Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	64		55
Acquisitions (dispositions), net	0		4
Actual return on plan assets
Relating to assets sold during the reporting period	4		2
Relating to assets still held at the reporting date	4		3
Fair value of plan assets at end of year	72		64
Fair Value, Inputs, Level 3 [Member] | Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	78		72
Acquisitions (dispositions), net	2		2
Actual return on plan assets
Relating to assets sold during the reporting period	0		0
Relating to assets still held at the reporting date	6		4
Fair value of plan assets at end of year	$ 86		$ 78

[1] Amount excludes net receivables of $2 million for 2013 and $4 million for 2012, primarily related to Level 1 investments.