Change in Benefit Obligations (Detail) - USD ($)		3 Months Ended			6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014		Jun. 30, 2015		Jun. 30, 2014
Pension Plans, Defined Benefit
Defined Benefit Plan, Service Cost	[1]	$ 1,000,000	$ 1,000,000		$ 2,000,000		$ 2,000,000
Defined Benefit Plan, Interest Cost		29,000,000	31,000,000	[1]	58,000,000	[1]	62,000,000	[1]
Defined Benefit Plan, Expected Return on Plan Assets	[1]	(52,000,000)	(50,000,000)		(103,000,000)		(100,000,000)
Defined Benefit Plan, Amortization of Gains (Losses)	[1]	6,000,000	4,000,000		11,000,000		8,000,000
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)		0	0		0		0
Defined Benefit Plan, Net Periodic Benefit Cost		(16,000,000)	(14,000,000)		(32,000,000)		(28,000,000)
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan, Service Cost		0	0		0		0
Defined Benefit Plan, Interest Cost		1,000,000	1,000,000		1,000,000		2,000,000
Defined Benefit Plan, Expected Return on Plan Assets		(1,000,000)	(2,000,000)		(2,000,000)		(3,000,000)
Defined Benefit Plan, Amortization of Gains (Losses)		0	0		0		0
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)		(2,000,000)	(1,000,000)		(3,000,000)		(3,000,000)
Defined Benefit Plan, Net Periodic Benefit Cost		$ (2,000,000)	$ (2,000,000)		$ (4,000,000)		$ (4,000,000)

[1] Administrative fees are recognized in service cost for each of the periods presented.