Available for Sale Marketable Securities in Unrealized Position (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	$ 20,170	$ 25,595
Less than 12 Months, Unrealized Loss	(46)	(31)
12 Months or Longer, Fair Value	5,528
12 Months or Longer, Unrealized Loss	(3)
Total, Fair Value	25,698	25,595
Total, Unrealized Loss	(49)	(31)
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	20,170	22,169
Less than 12 Months, Unrealized Loss	(46)	(30)
12 Months or Longer, Fair Value	5,528
12 Months or Longer, Unrealized Loss	(3)
Total, Fair Value	25,698	22,169
Total, Unrealized Loss	$ (49)	(30)
United States government agency securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value		3,426
Less than 12 Months, Unrealized Loss		(1)
12 Months or Longer, Fair Value		0
12 Months or Longer, Unrealized Loss		0
Total, Fair Value		3,426
Total, Unrealized Loss		$ (1)