Revenue - Summary of Amortization Expense Related to Net Capitalized Commission Asset (Detail)	6 Months Ended
	Jun. 30, 2018 USD ($)
Revenue from Contract with Customer [Abstract]
2018 (July 1, 2018 to December 31, 2018)	$ 1,021,000
2019	1,259,000
2020	578,000
2021	192,000
2022	6,000
Total	$ 3,056,000