Summary of Business and Significant Accounting Policies - Additional Information (Detail)			3 Months Ended		9 Months Ended
	Oct. 05, 2017 shares	Jan. 01, 2017 USD ($)	Sep. 30, 2017 USD ($) shares	Jun. 30, 2017 USD ($)	Sep. 30, 2017 USD ($) shares	Sep. 30, 2016 USD ($)	Oct. 04, 2017 shares	Dec. 31, 2016 USD ($) shares
Summary Of Significant Accounting Policies [Line Items]
Incorporation date					Mar. 31, 2006
Common stock, shares authorized | shares			142,857,000		142,857,000			142,857,000
Allowance for doubtful accounts			$ 3,628,000		$ 3,628,000			$ 3,510,000
Allowance for potential customer credits			1,042,000		1,042,000			1,947,000
Impairment of goodwill			0	$ 2,797,000
Impairment losses on long-lived assets					0	$ 0
Out-of-period revenue adjustment					$ 400,000
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			$ 10,768,000		$ 10,768,000			$ 15,657,000
Subsequent Event [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of fractional shares issued in connection with reverse stock split | shares	0
Common stock, shares authorized | shares	142,857,000						500,000,000
Subsequent Event [Member] | Common Stock [Member]
Summary Of Significant Accounting Policies [Line Items]
Reverse stock split of common stock, description	On October 5, 2017, the Company effected a reverse stock split of its outstanding common stock. As a result of the reverse stock split, each seven outstanding shares of the Company’s common stock was combined into one outstanding share of common stock, without any change in par value. The common stock began trading on the New York Stock Exchange on a split-adjusted basis on October 6, 2017. No fractional shares were issued in connection with the reverse stock split and the Company will pay in cash the fair value of such fractional shares.
Reverse stock split of common stock, conversion ratio	0.143