Fair Value Measurements - Fair Values and Unrealized Losses on Securities Available-for-Sale (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Available For Sale Securities [Line Items]
Less than Twelve Months, Estimated fair value	$ 70,651	$ 22,626
Less than Twelve Months, Gross unrealized losses	(270)	(31)
Estimated fair value, Total	70,651	22,626
Gross unrealized losses, Total	(270)	(31)
Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than Twelve Months, Estimated fair value	70,651	20,487
Less than Twelve Months, Gross unrealized losses	(270)	(29)
Estimated fair value, Total	70,651	20,487
Gross unrealized losses, Total	$ (270)	(29)
Municipal Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than Twelve Months, Estimated fair value		2,139
Less than Twelve Months, Gross unrealized losses		(2)
Estimated fair value, Total		2,139
Gross unrealized losses, Total		$ (2)