Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Income Taxes [Line Items]
Net deferred tax assets	$ 7,562,000
Net deferred tax liabilities	2,645,000	27,449,000
Federal net operating loss carry forwards	87,200,000
Federal net operating loss, valuation allowances released	72,600,000
Federal net operating loss, deferred tax benefit	$ 36,600,000