Fair Value Measurements (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Level 1
Assets:
Total assets	$ 2,010	$ 1,895
Level 2
Assets:
Total assets	0	0
Level 3
Assets:
Total assets	0	0
Cash Equivalents | Level 1
Assets:
Total assets	2,010	1,895
Cash Equivalents | Level 2
Assets:
Total assets	0	0
Cash Equivalents | Level 3
Assets:
Total assets	$ 0	$ 0