Fair Value Measurements - Fair Values and Unrealized Losses on Securities Available-for-Sale (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Estimated fair value	$ 4,937
Less than Twelve Months, Gross unrealized losses	(6)
Twelve Months or More, Estimated fair value
Twelve Months or More, Gross unrealized losses
Estimated fair value, Total	4,937
Gross unrealized losses, Total	(6)
Municipal securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Estimated fair value	2,780
Less than Twelve Months, Gross unrealized losses	(4)
Twelve Months or More, Estimated fair value
Twelve Months or More, Gross unrealized losses
Estimated fair value, Total	2,780
Gross unrealized losses, Total	(4)
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Estimated fair value	2,157
Less than Twelve Months, Gross unrealized losses	(2)
Twelve Months or More, Estimated fair value
Twelve Months or More, Gross unrealized losses
Estimated fair value, Total	2,157
Gross unrealized losses, Total	$ (2)