Loans - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans net of unearned discount and deferred loan fees	$ 1,200,000		$ 1,200,000		$ 7,500,000
Non-covered loans	11,197,315,000		11,197,315,000		9,527,797,000
Outstanding contractual principal balances	365,100,000		365,100,000		399,600,000
Non-interest income	7,000,000	2,700,000	13,600,000	7,100,000
Other non-interest income	7,400,000		7,400,000
Combined loan-to-value, ratio home equity loan	75.00%		75.00%
TDRs not reported as non-accrual loans	113,600,000		113,600,000		101,000,000
Non-performing TDRs	27,800,000		27,800,000		15,500,000
Specific reserves for loan losses			9,500,000	1,900,000
Covered By Fdic Loss Share [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-interest income	6,000,000
Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unsecured loans	395,500,000		395,500,000		337,700,000
Commercial Portfolio Segment | Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired loans	250,000		250,000
Consumer Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	1,433,893,000		1,433,893,000		1,378,728,000
Unsecured loans	85,200,000		85,200,000		66,500,000
Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unsecured loans	8,500,000		8,500,000		9,100,000
PCI Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	$ 1,200,000,000		$ 1,200,000,000