Loans - Summary of Composition of Troubled Debt Restructuring Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	$ 42,095	$ 83,969
Other Loans Held for Sale [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	41,319	69,791
Loans, Gross [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	776	14,178
Performing Troubled Debt Restructured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	30,154	45,557
Performing Troubled Debt Restructured Loans [Member] | Other Loans Held for Sale [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	30,154	37,191
Performing Troubled Debt Restructured Loans [Member] | Loans, Gross [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans		8,366
Non Performing Troubled Debt Restructured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	3,124	9,546
Non Performing Troubled Debt Restructured Loans [Member] | Other Loans Held for Sale [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	3,124	9,546
Non Performing Other Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	3,404	28,866
Non Performing Other Loans [Member] | Other Loans Held for Sale [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	2,628	23,054
Non Performing Other Loans [Member] | Loans, Gross [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	776	5,812
Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	5,413
Other [Member] | Other Loans Held for Sale [Member]
Financing Receivable, Recorded Investment [Line Items]
Total impaired loans	$ 5,413