Acquisitions - Summary of Preliminary Allocation of Purchase Price to Fair Value of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Jul. 06, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets:
Goodwill	$ 85,165		$ 76,169	$ 73,193
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Assets:
Cash		$ 463
Accounts receivable		738
Prepaids and other current assets		487
Goodwill		9,513
Acquired intangible assets		4,780
Other assets		75
Total assets		16,056
Liabilities:
Accounts payable and accrued liabilities		837
Contract liabilities		298
Deferred tax liability		825
Total liabilities		1,960
Net assets acquired		$ 14,096