Summary of Business and Significant Accounting Policies - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Summary Of Significant Accounting Policies [Line Items]
Incorporation date	Mar. 31, 2006
Allowance for doubtful accounts	$ 3,597,000		$ 3,510,000
Allowance for potential customer credits	1,759,000		1,947,000
Goodwill impairment	0	$ 0
ASU 2016-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Increase in valuation allowance	$ 1,423,000
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Intangible assets amortized useful lives	2 years
Minimum [Member] | Subscription arrangement [Member]
Summary Of Significant Accounting Policies [Line Items]
Length of subscription agreements	1 year
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Intangible assets amortized useful lives	6 years
Money Market Funds [Member] | Level 1 [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash equivalents - money market funds	$ 11,688,000		$ 15,657,000