Fair Value of Financial Assets and Liabilities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Assets:
Marketable securities	$ 82,187	$ 5,891
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	9,060	10,012
Marketable securities	82,187	5,891
Total assets measured at fair value	91,247	15,903
Recurring | Level 1
Assets:
Cash equivalents	8,810	10,012
Total assets measured at fair value	8,810	10,012
Recurring | Level 2
Assets:
Cash equivalents	250
Marketable securities	82,187	5,891
Total assets measured at fair value	$ 82,437	$ 5,891