Pension Benefits - Reconciliation of Fair Value Balances for Net Assets (Detail) (USD $) In Millions, unless otherwise specified					12 Months Ended
	Dec. 31, 2013 Pension Benefits [Member]	Dec. 31, 2012 Pension Benefits [Member]	Dec. 31, 2011 Pension Benefits [Member]	Dec. 31, 2010 Pension Benefits [Member]	Dec. 31, 2013 Real Estate [Member]	Dec. 31, 2012 Real Estate [Member] Pension Benefits [Member]	Dec. 31, 2013 Private Equity [Member]	Dec. 31, 2012 Private Equity [Member] Pension Benefits [Member]	Dec. 31, 2012 Corporate Bonds Debt [Member] Pension Benefits [Member]	Dec. 31, 2012 Structured Assets Debt [Member] Pension Benefits [Member]	Dec. 31, 2012 Other Fixed Income Debt [Member] Pension Benefits [Member]	Dec. 31, 2013 Investments [Member]	Dec. 31, 2012 Investments [Member] Pension Benefits [Member]	Dec. 31, 2013 Funds for Retiree Health Benefits [Member]	Dec. 31, 2012 Funds for Retiree Health Benefits [Member] Pension Benefits [Member]	Dec. 31, 2013 Investments (Excluding Funds for Retiree Health Benefits) [Member]	Dec. 31, 2012 Investments (Excluding Funds for Retiree Health Benefits) [Member] Pension Benefits [Member]	Dec. 31, 2013 Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	$ 10,755	$ 9,135	$ 7,800	$ 7,721	$ 833	$ 572	$ 20		$ 94	$ 13	$ 29	$ 853	$ 708	$ (31)	$ (28)	$ 822	$ 680
Assets Still Held at Reporting Date - Unrealized Gains/(Losses)					114	48	5	1				125	49	(3)	(2)	122	47	6
Assets Sold During the Year - Realized Gains/(Losses)					1	1				(6)		1	(5)			1	(5)
Purchases Sales and Settlements					114	212	42	19	(33)		(6)	356	192	(8)	(4)	348	188	200
Transfer In/(Out) of Level 3									(61)	(7)	(23)		(91)		3		(88)
FAIR VALUE OF PLAN ASSETS AT END OF YEAR	$ 10,755	$ 9,135	$ 7,800	$ 7,721	$ 1,062	$ 833	$ 67	$ 20				$ 1,335	$ 853	$ (42)	$ (31)	$ 1,293	$ 822	$ 206