Summary of Expiration Periods and Corresponding Valuation Allowances for Deferred Tax Assets related to Net Operating/Capital Loss and Tax Credit Carryforwards (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Gross deferred tax asset	$ 12,300
Valuation allowance	(5,600)
Net deferred tax asset	6,700
Expiration Period 2013 - 2017
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Gross deferred tax asset	700
Valuation allowance	(500)
Net deferred tax asset	200
Expiration Period 2018 - 2027
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Gross deferred tax asset	800
Valuation allowance	(500)
Net deferred tax asset	300
Expiration Period 2028 - 2032
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Gross deferred tax asset	5,900
Valuation allowance	(1,300)
Net deferred tax asset	4,600
Indefinite
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Gross deferred tax asset	4,900
Valuation allowance	(3,300)
Net deferred tax asset	$ 1,600