Fair Value Measurement (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets:
Marketable securities	$ 74,459	$ 61,868
Foreign exchange contracts	0	6
Government bonds
Assets:
Marketable securities	497	497
Certificates of deposits
Assets:
Marketable securities	747
Corporate bonds
Assets:
Marketable securities	73,215	61,371
Level II
Assets:
Foreign exchange contracts		6
Level II | Government bonds
Assets:
Marketable securities	497	497
Level II | Certificates of deposits
Assets:
Marketable securities	747
Level II | Corporate bonds
Assets:
Marketable securities	$ 73,215	$ 61,371