Cash and cash equivalents - Schedule of Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Cash and Cash Equivalents [Abstract]
Cash	$ 7,895	$ 2,133
Cash equivalents	14,575	37,393
Cash and cash equivalents	$ 22,470	$ 39,526	$ 14,916	$ 14,906