Cash and cash equivalents - Schedule of Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Cash and Cash Equivalents [Abstract]
Cash	$ 4,073	$ 2,133
Cash equivalents	31,618	37,393
Cash and cash equivalents	$ 35,691	$ 39,526	$ 14,283	$ 14,906