Investment in Joint Venture - Summarized Balance Sheet Information of Unconsolidated Joint Venture (Detail) - Joint Venture [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Current assets	$ 47,600	$ 31,295
Non-current assets	24,763	22,522
Total assets	72,363	53,817
Current liabilities	26,165	13,549
Total liabilities	$ 26,165	$ 13,549