Cash and cash equivalents - Schedule of Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Cash and Cash Equivalents [Abstract]
Cash	$ 3,633	$ 8,351
Cash equivalents	11,283	6,555
Cash and cash equivalents	$ 14,916	$ 14,906	$ 17,896	$ 11,006