Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Summary Of Significant Accounting Policies [Line Items]
Currency translation adjustment	$ (39)	$ (80)	$ 51	$ 166
Net carrying value of software developed	184	185
Vehicle interest income	18	13	10
Advertising expense	127	123	112
Investments in joint ventures	36	36
Aggregate realized gain from the sale of investments			7
Retained risks of liability to third parties	437	413
Workers compensation liabilities	71	70
Business Acquisition, Transaction Costs		18
Business Combination, Contingent Consideration, Liability		9
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability		13
Business Combination, Contingent Consideration, Liability, Favorable Currency Exchange Rate Movements		4
Gain or loss of currency transactions	6	$ 11	$ 9
Employee Service Share Based Compensation Incremental Tax Benefit To Be Realized From Exercise Of Stock Awards	$ 56