Accounts Receivable - Summary of Accounts Receivable (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contract receivables	$ 65,453	$ 48,826
Allowance for doubtful accounts	(2,925)	(2,897)
Total accounts receivable	72,963	53,225
Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade receivables	$ 10,435	$ 7,296