Revenue Recognition- Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Jan. 01, 2018
Deferred Revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred revenues (Short-term contract liability)	$ 1,295,000
ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impact to revenues	1,963,000
Capitalized contract acquisition costs		$ 239,000
Capitalized contract cost, amortization	11,000
Impairment loss in relation to costs capitalized	0
ASU 2014-09 | Accrued Revenues
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New accounting pronouncement or change in accounting principle cumulative effect of change on equity or net assets	$ 6,611,000
ASU 2014-09 | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New accounting pronouncement or change in accounting principle cumulative effect of change on equity or net assets		$ 8,555,000