Fair Value Measurements - Fair Values and Unrealized Losses on Securities Available-for-Sale (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Available For Sale Securities [Line Items]
Less than Twelve Months, Estimated fair value	$ 22,626	$ 15,683
Less than Twelve Months, Gross unrealized losses	(31)	(19)
Estimated fair value, Total	22,626	15,683
Gross unrealized losses, Total	(31)	(19)
Municipal Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than Twelve Months, Estimated fair value	2,139	4,955
Less than Twelve Months, Gross unrealized losses	(2)	(6)
Estimated fair value, Total	2,139	4,955
Gross unrealized losses, Total	(2)	(6)
Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than Twelve Months, Estimated fair value	20,487	10,728
Less than Twelve Months, Gross unrealized losses	(29)	(13)
Estimated fair value, Total	20,487	10,728
Gross unrealized losses, Total	$ (29)	$ (13)