Summary of Significant Accounting Policies - Summary of Financial Statement Revision of Prior Interim Period Adjustments on Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accounts receivable	$ 5,289	$ 4,921	$ 6,968	$ 7,017	$ 7,197
Total Current Assets	26,386	25,503	23,783	22,924	32,227
Total Assets	52,208	53,391	53,005	51,372	60,092
Deferred revenue	914	979	1,003	673	754
Total Current Liabilities	5,948	5,256	7,064	6,007	6,297
Total Liabilities	10,790	10,577	12,848	11,926	12,664
Accumulated deficit	(238,272)	(237,776)	(241,520)	(241,510)	(241,662)
Total Shareholders' Equity	40,868	42,264	39,607	38,896	46,878	31,365	20,631
Total Liabilities & Shareholders' Equity	52,208	53,391	53,005	51,372	60,092
As Previously Reported [Member]
Accounts receivable		5,252	7,209	7,258
Total Current Assets		25,834	24,024	23,165
Total Assets		53,722	53,246	51,613
Deferred revenue		904	764	637
Total Current Liabilities		5,181	6,825	5,971
Total Liabilities		10,502	12,609	11,890
Accumulated deficit		(237,370)	(241,040)	(241,233)
Total Shareholders' Equity		42,670	40,087	39,173
Total Liabilities & Shareholders' Equity		53,722	53,246	51,613
Adjustment [Member]
Accounts receivable		(331)	(241)	(241)
Total Current Assets		(331)	(241)	(241)
Total Assets		(331)	(241)	(241)
Deferred revenue		75	239	36
Total Current Liabilities		75	239	36
Total Liabilities		75	239	36
Accumulated deficit		(406)	(480)	(277)
Total Shareholders' Equity		(406)	(480)	(277)
Total Liabilities & Shareholders' Equity		$ (331)	$ (241)	$ (241)