Retirement Plans - Fair Value of Plan's Financial Assets (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	$ 2,145	$ 1,763
Cash and Short-term Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	75	39
U.S. Equities (domestic) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	729	534
International Equities (non-U.S.) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	252	209
Global Equities (domestic and non-U.S.) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	216	179
Treasury and Government Issued [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	170	186
Government Related [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	9	8
Mortgage-backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	110	96
Corporate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	127	111
Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	291	255
Private Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	89	75
Real Estate Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	57	54
Diversified Commodities Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	20	17
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	833	612
Level 1 [Member] | Cash and Short-term Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	3	2
Level 1 [Member] | U.S. Equities (domestic) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	729	534
Level 1 [Member] | International Equities (non-U.S.) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	81	61
Level 1 [Member] | Global Equities (domestic and non-U.S.) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	8	5
Level 1 [Member] | Treasury and Government Issued [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets
Level 1 [Member] | Government Related [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets
Level 1 [Member] | Mortgage-backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets
Level 1 [Member] | Corporate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	2	1
Level 1 [Member] | Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets
Level 1 [Member] | Private Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets
Level 1 [Member] | Real Estate Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	10	9
Level 1 [Member] | Diversified Commodities Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	882	774
Level 2 [Member] | Cash and Short-term Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	72	37
Level 2 [Member] | U.S. Equities (domestic) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets
Level 2 [Member] | International Equities (non-U.S.) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	171	148
Level 2 [Member] | Global Equities (domestic and non-U.S.) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	208	174
Level 2 [Member] | Treasury and Government Issued [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	169	184
Level 2 [Member] | Government Related [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	9	8
Level 2 [Member] | Mortgage-backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	109	96
Level 2 [Member] | Corporate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	124	110
Level 2 [Member] | Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets
Level 2 [Member] | Private Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets
Level 2 [Member] | Real Estate Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets
Level 2 [Member] | Diversified Commodities Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	20	17
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	430	377	317
Level 3 [Member] | Cash and Short-term Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets
Level 3 [Member] | U.S. Equities (domestic) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets
Level 3 [Member] | International Equities (non-U.S.) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets
Level 3 [Member] | Global Equities (domestic and non-U.S.) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets
Level 3 [Member] | Treasury and Government Issued [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	1	2
Level 3 [Member] | Government Related [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets
Level 3 [Member] | Mortgage-backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	1
Level 3 [Member] | Corporate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	1
Level 3 [Member] | Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	291	255	211
Level 3 [Member] | Private Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	89	75	58
Level 3 [Member] | Real Estate Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets	47	45	44
Level 3 [Member] | Diversified Commodities Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of the plan's financial assets