Investment in Joint Venture - Summarized Income Statement Information of Unconsolidated Joint Venture (Detail) - Joint Venture [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Net sales	$ 74,805	$ 65,756	$ 55,962
Cost of sales	57,514	44,530	37,283
Income from operations	13,659	16,268	13,972
Net income	$ 11,442	$ 13,702	$ 11,525