Business Segments - Summary of Operating Results by Reportable Segment (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
Revenue:
Total revenue	$ 1,070	$ 1,113	$ 3,099	$ 3,255
Operating profit:
Total operating profit	50	63	155	174
Operating profit %:
Total operating profit %	4.70%	5.70%	5.00%	5.30%
United States (Member)
Revenue:
Total revenue	748	732	2,114	2,187
Operating profit:
Total operating profit	28	36	86	109
Operating profit %:
Total operating profit %	3.70%	4.90%	4.10%	5.00%
Canada (Member)
Revenue:
Total revenue	173	191	489	578
Operating profit:
Total operating profit	14	13	33	35
Operating profit %:
Total operating profit %	8.10%	6.80%	6.70%	6.10%
International [Member]
Revenue:
Total revenue	149	190	496	490
Operating profit:
Total operating profit	$ 8	$ 14	$ 36	$ 30
Operating profit %:
Total operating profit %	5.40%	7.40%	7.30%	6.10%