Dental Loan Portfolio - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans to dental professionals	$ 270,782	$ 208,489
Percentage of total outstanding loans	31.10%	25.40%
Government guarantees	$ 18,834	$ 21,048
Percentage of outstanding dental loan	6.96%	10.01%