Income Tax (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Income Tax Expense (Benefit)	$ 2,630,000	$ 4,241,000
Deferred Tax Asset, Write-Down		2,100,000
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate	33.36%	70.92%
Effective Income Tax Rate Reconciliation, Tax Credits		35.62%
Deferred Tax Assets, Net	8,300,000
Deferred Tax Liabilities, Net			$ 3,600,000