Capital Lease Obligations - Additional Information (Detail) - Capital Lease for Acquisition of Computer Equipment [Member] $ in Thousands	Mar. 31, 2018 USD ($) Installment	Dec. 31, 2017 USD ($)
Line of Credit Facility [Line Items]
Net book value of equipment under capital leases | $	$ 2,549	$ 2,861
Remaining principal balance payable | $	$ 2,785	$ 3,103
Minimum [Member]
Line of Credit Facility [Line Items]
Effective annual interest rate	5.20%
Number of monthly installments | Installment	36
Maximum [Member]
Line of Credit Facility [Line Items]
Effective annual interest rate	7.90%
Number of monthly installments | Installment	48