Fair Value Measurements - Fair Values and Unrealized Losses on Securities Available-for-Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule Of Available For Sale Securities [Line Items]
Less than Twelve Months, Estimated fair value	$ 37,085	$ 22,626
Less than Twelve Months, Gross unrealized losses	(68)	(31)
Estimated fair value, Total	37,085	22,626
Gross unrealized losses, Total	(68)	(31)
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)
Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than Twelve Months, Estimated fair value	37,085	20,487
Less than Twelve Months, Gross unrealized losses	(68)	(29)
Estimated fair value, Total	37,085	20,487
Gross unrealized losses, Total	$ (68)	$ (29)