Investments - Summary of Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	$ 1,498	$ 8,483
Unrealized Losses, Less than 12 Months	3	12
Fair Value, 12 Months or More	485	0
Unrealized Losses, 12 Months or More	2	0
Fair Value	1,983	8,483
Unrealized Losses	5	12
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		3,994
Unrealized Losses, Less than 12 Months		1
Fair Value, 12 Months or More		0
Unrealized Losses, 12 Months or More		0
Fair Value		3,994
Unrealized Losses		1
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	1,498	4,439
Unrealized Losses, Less than 12 Months	3	11
Fair Value, 12 Months or More	485	0
Unrealized Losses, 12 Months or More	2	0
Fair Value	1,983	4,439
Unrealized Losses	$ 5	$ 11