Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 USD ($) Installment	Dec. 31, 2015 USD ($)
Schedule Of Significant Accounting Policies [Line Items]
Maximum maturity period of highly liquid investments	3 months
Allowances for doubtful accounts | $	$ 527,000	$ 344,000
Accruals for premium deficiency | $	$ 0	$ 0
Minimum [Member]
Schedule Of Significant Accounting Policies [Line Items]
Short-term investment maturity period	3 months
Useful life of property and equipment	3 years
Number of installments to pay policy premiums | Installment	2
Maximum [Member]
Schedule Of Significant Accounting Policies [Line Items]
Useful life of property and equipment	27 years 6 months
Number of installments to pay policy premiums | Installment	4