Investments - Summary of Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	$ 5,803	$ 11,779
Unrealized Losses, Less than 12 Months	(5)	(40)
Fair Value, 12 Months or More	160	284
Unrealized Losses, 12 Months or More	0	(2)
Fair Value	5,963	12,063
Unrealized Losses	(5)	(42)
U.S. Treasury securities, obligations of U.S. Government agencies and Municipals
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	5,102	8,998
Unrealized Losses, Less than 12 Months	(5)	(26)
Fair Value, 12 Months or More	0	0
Unrealized Losses, 12 Months or More	0	0
Fair Value	5,102	8,998
Unrealized Losses	(5)	(26)
Foreign government
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months		50
Unrealized Losses, Less than 12 Months		0
Fair Value, 12 Months or More		0
Unrealized Losses, 12 Months or More		0
Fair Value		50
Unrealized Losses		0
Corporate debt
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	701	2,731
Unrealized Losses, Less than 12 Months	0	(14)
Fair Value, 12 Months or More	160	284
Unrealized Losses, 12 Months or More	0	(2)
Fair Value	861	3,015
Unrealized Losses	$ 0	$ (16)