Available-for-Sale Marketable Securities in Unrealized Position (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	$ 20,082	$ 20,170
Less than 12 Months, Unrealized Loss	(17)	(46)
12 Months or Longer, Fair Value		5,528
12 Months or Longer, Unrealized Loss		(3)
Total, Fair Value	20,082	25,698
Total, Unrealized Loss	(17)	(49)
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	20,082	20,170
Less than 12 Months, Unrealized Loss	(17)	(46)
12 Months or Longer, Fair Value		5,528
12 Months or Longer, Unrealized Loss		(3)
Total, Fair Value	20,082	25,698
Total, Unrealized Loss	$ (17)	$ (49)