Government Programs - Additional Information (Detail) AUD in Thousands	1 Months Ended					3 Months Ended				6 Months Ended
	May 31, 2017 USD ($)	Jul. 31, 2016 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2016 AUD	Sep. 30, 2015 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2017 AUD	Jun. 30, 2016 USD ($)	Jun. 30, 2016 AUD	Jun. 30, 2017 USD ($)	Jun. 30, 2017 AUD	Jun. 30, 2016 USD ($)	Jun. 30, 2016 AUD	Jun. 30, 2017 AUD	Dec. 31, 2016 USD ($)	Dec. 31, 2016 AUD
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development tax incentive receivable						$ 2,881,000				$ 2,881,000					$ 2,241,000
SBIR Grant [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reduction of research and development expenses related to tax						20,000				20,000		$ 69,000
Research and development grants	$ 1,300,000	$ 219,000			$ 224,000
Grants receivable						19,000				19,000					100,000
Overseas Findings [Member] | Australian Taxation Office [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development tax incentive receivable						2,900,000				2,900,000				AUD 3,700	$ 2,200,000	AUD 3,100
Deferred tax incentive			$ 181,000	AUD 237
Research and Development Tax Incentive [Member] | Australian Taxation Office [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reduction of research and development expenses related to tax						$ 377,000	AUD 501	$ 498,000	AUD 666	$ 480,000	AUD 635	$ 1,000,000	AUD 1,400