Loans - Summary of Composition of Non-Accrual Loans by Portfolio Segment (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Accrual Loans	$ 137,615	$ 103,270
Commercial loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Accrual Loans	112,517	73,255
Residential mortgage loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Accrual Loans	18,649	25,043
Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Accrual Loans	6,449	4,972
Originated loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Accrual Loans	103,428	83,307
Originated loans [Member] | Commercial loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Accrual Loans	91,908	55,046
Originated loans [Member] | Residential mortgage loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Accrual Loans	7,705	24,406
Originated loans [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Accrual Loans	3,815	3,855
Acquired loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Accrual Loans	30,087	1,117
Acquired loans [Member] | Commercial loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Accrual Loans	16,902
Acquired loans [Member] | Residential mortgage loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Accrual Loans	10,551
Acquired loans [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Accrual Loans	2,634	1,117
Covered loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Accrual Loans	4,100	18,846
Covered loans [Member] | Commercial loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Accrual Loans	3,707	18,209
Covered loans [Member] | Residential mortgage loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Accrual Loans	$ 393	$ 637