Summarized Financial Information of Unconsolidated Joint Ventures (Sales, Profit, and Income) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Net sales	$ 54,597	$ 47,321	$ 43,438
Gross profit	21,462	16,829	11,993
Net income	$ 9,796	$ 8,292	$ 5,753