Pension and Other Postretirement Benefits - Reconciliation of Fair Value Measurements Using Significant Unobservable Inputs (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	$ 2,484	$ 2,360
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	174	165
Transfer in (out) of Level 3	(3)	2
Purchases	4	15
Sales	(19)	(5)
Settlements	(12)	(13)
Unrealized gain/(loss)	7	1
Realized gain	9	9
Fair value of plan assets at end of year	160	174
Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	31	27
Transfer in (out) of Level 3
Purchases		4
Sales	(5)	(4)
Settlements		(1)
Unrealized gain/(loss)	7	4
Realized gain	2	1
Fair value of plan assets at end of year	35	31
Significant Unobservable Inputs (Level 3) [Member] | Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	13	9
Transfer in (out) of Level 3	(3)	2
Purchases		2
Sales	(1)	(1)
Settlements	2	1
Unrealized gain/(loss)
Realized gain
Fair value of plan assets at end of year	11	13
Significant Unobservable Inputs (Level 3) [Member] | Private Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	56	64
Transfer in (out) of Level 3
Purchases	2	4
Sales
Settlements	(4)	(8)
Unrealized gain/(loss)	(7)	(11)
Realized gain	6	7
Fair value of plan assets at end of year	53	56
Significant Unobservable Inputs (Level 3) [Member] | Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	74	65
Transfer in (out) of Level 3
Purchases	2	5
Sales	(13)
Settlements	(10)	(5)
Unrealized gain/(loss)	7	8
Realized gain	1	1
Fair value of plan assets at end of year	$ 61	$ 74