Loans - Summary of Composition of Troubled Debt Restructuring Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	$ 43,920	$ 42,095
Other Loans Held for Sale [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	43,144	41,319
Loans, Gross [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	776	776
Performing Troubled Debt Restructured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	24,169	30,154
Performing Troubled Debt Restructured Loans [Member] | Other Loans Held for Sale [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	24,169	30,154
Performing Troubled Debt Restructured Loans [Member] | Loans, Gross [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans
Non Performing Troubled Debt Restructured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	2,829	3,124
Non Performing Troubled Debt Restructured Loans [Member] | Other Loans Held for Sale [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	2,829	3,124
Non Performing Troubled Debt Restructured Loans [Member] | Loans, Gross [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans
Non Performing Other Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	5,948	3,404
Non Performing Other Loans [Member] | Other Loans Held for Sale [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	5,172	2,628
Non Performing Other Loans [Member] | Loans, Gross [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	776	776
Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	10,974	5,413
Other [Member] | Other Loans Held for Sale [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	10,974	5,413
Other [Member] | Loans, Gross [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans