Fair Value - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) (Fair Value, Measurements, Recurring [Member], Significant Unobservable Inputs (Level 3) [Member], Corporate Bonds Available for Sale [Member], USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Corporate Bonds Available for Sale [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, January 1	$ 443	$ 451
Total unrealized gain (loss) included in income
Total unrealized gain (loss) included in other comprehensive income	8
Balance, September 30	$ 451	$ 451