Changes in and Reclassification out of Accumulated Other Comprehensive Loss by Component - Summary of Reclassification of Accumulated Other Comprehensive Loss by Component (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amount reclassified from accumulated other comprehensive income, net of tax	$ 4		$ 7		$ 12		$ 19
Interest Rate Swap
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amount reclassified from accumulated other comprehensive income, before tax	4		4		12		12
Amount reclassified from accumulated other comprehensive income, tax	2		1		5		4
Amount reclassified from accumulated other comprehensive income, net of tax	2		3		7		8
Actuarial loss
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amount reclassified from accumulated other comprehensive income, before tax	3	[1]	5	[1]	9	[2]	14	[2]
Amount reclassified from accumulated other comprehensive income, tax	1		1		4		3
Amount reclassified from accumulated other comprehensive income, net of tax	$ 2		$ 4		$ 5		$ 11

[1] This accumulated other comprehensive loss component is included in the computation of net periodic pension cost.

[2] (a) This accumulated other comprehensive loss component is included in the computation of net periodic pension cost.