Pension Plans, Other Postretirement Benefits, and Defined-Contribution Plans - Fair Value of Pension Plan Assets by Asset Category and Input Level Table (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Liabilities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ (11)		$ (12)
Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,469	[1]	1,321	[2]
Fair Value, Inputs, Level 1 [Member] | Liabilities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(11)		(12)
Fair Value, Inputs, Level 1 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	508	[1]	456	[2]
Table Text Block Supplement [Abstract]
Net receivables (payables) related to investments	4		(1)
Fair Value, Inputs, Level 2 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	742	[1]	674	[2]
Fair Value, Inputs, Level 3 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	219	[1]	191	[2]	99
Cash and Cash Equivalents [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	59		91
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	23		37
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	36		54
Mortgage-backed Securities [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	63		66
Mortgage-backed Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	63		66
U.S. Government Securities [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	54		50
U.S. Government Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			1
U.S. Government Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	54		49
Other Fixed-Income Securities [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	236	[3]	207	[3]
Other Fixed-Income Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	40	[3]	36	[3]
Other Fixed-Income Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	196	[3]	171	[3]
Equity Securities Domestic [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	422		359
Equity Securities Domestic [Member] | Fair Value, Inputs, Level 1 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	313		265
Equity Securities Domestic [Member] | Fair Value, Inputs, Level 2 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	109		94
Equity Securities International [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	350		294
Equity Securities International [Member] | Fair Value, Inputs, Level 1 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	112		91
Equity Securities International [Member] | Fair Value, Inputs, Level 2 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	238		203
Real Estate [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	124		109
Real Estate [Member] | Fair Value, Inputs, Level 2 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	46		37
Real Estate [Member] | Fair Value, Inputs, Level 3 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	78		72		9
Private Equity [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	64		55
Private Equity [Member] | Fair Value, Inputs, Level 3 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	64		55		41
Hedge Funds and Other Alternative Strategies Asset Position [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	97		90
Hedge Funds and Other Alternative Strategies Asset Position [Member] | Fair Value, Inputs, Level 1 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	20		26
Hedge Funds and Other Alternative Strategies Asset Position [Member] | Fair Value, Inputs, Level 3 [Member] | Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	77		64		49
Hedge Funds and Other Alternative Strategies Liability Position [Member] | Liabilities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(11)		(12)
Hedge Funds and Other Alternative Strategies Liability Position [Member] | Fair Value, Inputs, Level 1 [Member] | Liabilities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ (11)		$ (12)

[1] Amount excludes net receivables of $4 million, primarily related to Level 1 investments.

[2] Amount excludes net payables of $1 million, primarily related to Level 1 investments.

[3] Amounts include investments in diversified fixed-income collective investment funds with exposure to mortgage-backed securities, government-issued securities, corporate debt, and other fixed-income securities.