Commitments - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments Disclosure [Line Items]
Rent expense	$ 68,920	$ 62,294	$ 58,133
Short term committed purchase obligations	56,116
Contribution by employer for employee saving plan	$ 18,210	$ 9,681	$ 8,658
Buildings
Commitments Disclosure [Line Items]
Terms of operating leases expiring year	Dec. 31, 2028
Land
Commitments Disclosure [Line Items]
Terms of operating leases expiring year	Dec. 31, 2057