Components of Prepaid Expenses and Other (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	$ 10,654	$ 6,998
Prepaid expenses and other, long-term	2,674	6,846
Totals	13,328	13,844
CRO services
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	7,285	3,471
Prepaid expenses and other, long-term	1,152	5,077
Other clinical development
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	1,109	1,069
Prepaid expenses and other, long-term	1,077	1,243
Insurance
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	865	1,159
Prepaid expenses and other, long-term	28	40
Other
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	1,395	1,299
Prepaid expenses and other, long-term	$ 417	$ 486