Capitalized Interest - Summary of Interest Incurred, Capitalized and Expensed (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Interest Expense [Abstract]
Interest cost incurred	$ 5,814	$ 4,880	$ 11,405	$ 9,477
Interest capitalized		404	396	993
Interest expense	$ 5,814	$ 4,476	$ 11,009	$ 8,484