Supplemental Cash Flow Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Cash Flow Information [Abstract]
Taxes paid	$ 51,231	$ 47,289	$ 40,621
Non-cash investing and financing activities:
Fixed assets acquired with accounts payable or accrued liabilities	15,105	4,434	14,636
Fair value of option to purchase property	$ 3,936	$ 0	$ 0