Loans - Credit Risk Profile Based on Payment Activity (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit risk profile based on payment activity	$ 1,654,170	$ 1,607,370
Performing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit risk profile based on payment activity	1,647,721	1,602,398
Nonperforming [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit risk profile based on payment activity	6,449	4,972
Originated loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit risk profile based on payment activity	1,351,776	1,074,611
Originated loans [Member] | Performing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit risk profile based on payment activity	1,347,961	1,070,756
Originated loans [Member] | Nonperforming [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit risk profile based on payment activity	3,815	3,855
Consumer Acquired [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit risk profile based on payment activity	202,974	386,540
Consumer Acquired [Member] | Performing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit risk profile based on payment activity	200,340	385,423
Consumer Acquired [Member] | Nonperforming [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit risk profile based on payment activity	2,634	1,117
Covered loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit risk profile based on payment activity	99,420	146,219
Covered loans [Member] | Performing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit risk profile based on payment activity	$ 99,420	$ 146,219