Commitments - Additional Information (Detail) ft² in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	May 31, 2015 ft²	Feb. 28, 2015 ft²
Operating Leased Assets [Line Items]
Operating lease expiration year	2023
Rent expense | $	$ 1,283	$ 1,291	$ 742
Lease agreements | Lease property one
Operating Leased Assets [Line Items]
Operating lease facility area				33
Lease agreements | Lease property two
Operating Leased Assets [Line Items]
Operating lease facility area					42