Additional Cash Flow Information - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Supplemental Cash Flow Information [Abstract]
Income taxes paid	$ 65,688	$ 48,615
Interest paid	2,981	2,730
Acquired operating property by capital leases	14,760	$ 46,456
Acquired operating property by accruing in accounts payable	945
Unpaid capital expenditure	$ 1,988		$ 5,298