Troubled Debt Restructured Loans for Specific Segments of the Loan Portfolio (Detail) (USD $) In Thousands, unless otherwise specified																			12 Months Ended
	Jun. 30, 2012 Specific Allowance	Dec. 31, 2011 Specific Allowance	Jun. 30, 2012 Commercial Loan Specific Allowance	Dec. 31, 2011 Commercial Loan Specific Allowance	Dec. 31, 2011 All Other Specific Allowance	Jun. 30, 2012 Troubled Debt Restructuring	Dec. 31, 2011 Troubled Debt Restructuring	Jun. 30, 2012 Troubled Debt Restructuring Accrual Loans	Dec. 31, 2011 Troubled Debt Restructuring Accrual Loans	Dec. 31, 2011 Troubled Debt Restructuring Non Accrual Loans	Jun. 30, 2012 Troubled Debt Restructuring Commercial Loan	Dec. 31, 2011 Troubled Debt Restructuring Commercial Loan	Jun. 30, 2012 Troubled Debt Restructuring Commercial Loan Accrual Loans	Dec. 31, 2011 Troubled Debt Restructuring Commercial Loan Accrual Loans	Dec. 31, 2011 Troubled Debt Restructuring Commercial Loan Non Accrual Loans	Dec. 31, 2011 Troubled Debt Restructuring All Other	Dec. 31, 2011 Troubled Debt Restructuring All Other Accrual Loans	Dec. 31, 2011 Troubled Debt Restructuring All Other Non Accrual Loans	Dec. 31, 2011 Restructured Loans Subsequently Defaults	Dec. 31, 2011 Restructured Loans All Other Subsequently Defaults	Dec. 31, 2011 Commercial Portfolio Segment Commercial Investor Real Estate Specific Allowance	Jun. 30, 2012 Commercial Portfolio Segment Commercial Owner Occupied Real Estate Specific Allowance	Dec. 31, 2011 Commercial Portfolio Segment Commercial Owner Occupied Real Estate Specific Allowance	Dec. 31, 2011 Commercial Portfolio Segment Troubled Debt Restructuring Commercial Investor Real Estate	Dec. 31, 2011 Commercial Portfolio Segment Troubled Debt Restructuring Commercial Investor Real Estate Non Accrual Loans	Jun. 30, 2012 Commercial Portfolio Segment Troubled Debt Restructuring Commercial Owner Occupied Real Estate	Dec. 31, 2011 Commercial Portfolio Segment Troubled Debt Restructuring Commercial Owner Occupied Real Estate	Jun. 30, 2012 Commercial Portfolio Segment Troubled Debt Restructuring Commercial Owner Occupied Real Estate Accrual Loans	Dec. 31, 2011 Commercial Portfolio Segment Troubled Debt Restructuring Commercial Owner Occupied Real Estate Non Accrual Loans
Financing Receivable, Modifications [Line Items]
Loans Receivable						$ 1,737	$ 10,262	$ 1,737	$ 5,286	$ 4,976	$ 710	$ 2,165	$ 710	$ 1,696	$ 469	$ 4,353	$ 3,590	$ 763						$ 1,269	$ 1,269	$ 1,027	$ 2,475	$ 1,027	$ 2,475
Specific allowance	281	1,883	64	254	1,027																93	217	509
Loans Receivable																			$ 509	$ 509