Fair Value of Financial Assets and Liabilities (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Assets:
Marketable securities	$ 62,195	$ 82,187
Transfers from Level 1 to Level 2	0	0
Transfers from Level 2 to Level 1	0	0
Transfers into or out of Level 3	0	0
Recurring
Assets:
Cash equivalents	31,715	9,060
Marketable securities	62,195	82,187
Total assets measured at fair value	93,910	91,247
Recurring | Level 1
Assets:
Cash equivalents	27,708	8,810
Total assets measured at fair value	27,708	8,810
Recurring | Level 2
Assets:
Cash equivalents	4,007	250
Marketable securities	62,195	82,187
Total assets measured at fair value	$ 66,202	$ 82,437