Commitments and Contingencies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Purchase order outstanding	$ 11,097,000
Total annual rental expense	8,186,000	$ 6,738,000	$ 6,090,000
Total annual rental income	$ 1,116,000	$ 1,474,000	$ 1,911,000