Loans, Allowance for Loan Losses, and Credit Quality Indicators - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Guarantor Obligations [Line Items]
Outstanding loans to dental professionals	$ 270,782,000	$ 208,489,000
Percentage of total outstanding loans	31.10%	25.40%
Percentage of total loan portfolio	10.00%
Percentage of loan portfolio collateralized by real estate	62.10%
Valuation allowance for impaired loans	2,000	455,000
Recorded investment in impaired loans, net of government guarantees	9,493,000	30,094,000
Government guarantees	681,000	1,094,000
Average recorded investment for impaired loans	21,701,000	47,291,000	66,510,000
Interest income recognized on impaired loans	34,000	548,000	2,602,000
Recorded investment in nonaccrual status	9,361,000	26,594,000
Identified TDRs newly considered for impairment	6
Total recorded investment in receivables	806,000
Associated allowance for loan losses	2,000
Troubled Debt Restructurings [Member]
Guarantor Obligations [Line Items]
Recorded investment in nonaccrual status	2,336,000	4,091,000
Allowance for loan losses [Member]
Guarantor Obligations [Line Items]
Specific valuation allowance for impaired loans	2,000	455,000
Valuation allowance for impaired loans	10,174,000	31,187,000
Recorded investment in impaired loans, net of government guarantees	$ 9,493,000	$ 30,094,000
Minimum [Member]
Guarantor Obligations [Line Items]
Internal risk rating	1
Maximum [Member]
Guarantor Obligations [Line Items]
Internal risk rating	10