Fair Value Measurements - Fair Values and Unrealized Losses on Securities Available-for-Sale (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule Of Available For Sale Securities [Line Items]
Less than Twelve Months, Estimated fair value	$ 26,080	$ 22,626
Less than Twelve Months, Gross unrealized losses	(54)	(31)
Estimated fair value, Total	26,080	22,626
Gross unrealized losses, Total	(54)	(31)
Municipal Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than Twelve Months, Estimated fair value	3,097	2,139
Less than Twelve Months, Gross unrealized losses	(1)	(2)
Estimated fair value, Total	3,097	2,139
Gross unrealized losses, Total	(1)	(2)
Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than Twelve Months, Estimated fair value	22,983	20,487
Less than Twelve Months, Gross unrealized losses	(53)	(29)
Estimated fair value, Total	22,983	20,487
Gross unrealized losses, Total	$ (53)	$ (29)