Other Income (Expense) - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Component Of Other Income (Expense), Nonoperating [Line Items]
Other income (expense)	$ 1,034	$ 619	$ (874)
State Income Tax Benefit [Member]
Component Of Other Income (Expense), Nonoperating [Line Items]
Other income (expense)		470
Construction Litigation [Member]
Component Of Other Income (Expense), Nonoperating [Line Items]
Other income (expense)	1,554
Technology Investment [Member]
Component Of Other Income (Expense), Nonoperating [Line Items]
Other income (expense)	62	475	168
Legal Settlements And Miscellaneous Receivable Recoveries [Member]
Component Of Other Income (Expense), Nonoperating [Line Items]
Other income (expense)	43	274
Texas Franchise Tax [Member]
Component Of Other Income (Expense), Nonoperating [Line Items]
Other income (expense)	625	600	580
Corporate Impairment [Member]
Component Of Other Income (Expense), Nonoperating [Line Items]
Other income (expense)			1,165
Legal Settlement [Member]
Component Of Other Income (Expense), Nonoperating [Line Items]
Other income (expense)			517
Accrual Adjustment [Member]
Component Of Other Income (Expense), Nonoperating [Line Items]
Other income (expense)			$ 187