Allowance For Loan Losses and Credit Quality Information (Commercial Credit Exposure Credit Risk Profile By Internally Assigned Risk Rating) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	$ 2,167,932		$ 2,188,409
Commercial Loans	100.00%		100.00%
Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	75,322		145,639
Accrual [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	154,413		140,599
Non Accrual [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	20,786		61,131
Doubtful/Nonaccrual [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	4,612
Special Mention And Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	255,133		347,369
Commercial Loans	12.00%		16.00%
Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	1,912,799		1,841,040
Commercial Loans	88.00%		84.00%
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	698,205		1,459,456
Commercial [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	14,758		85,848
Commercial [Member] | Accrual [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	73,204		107,896
Commercial [Member] | Non Accrual [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	1,334		23,193
Commercial [Member] | Doubtful/Nonaccrual [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	2,245
Commercial [Member] | Special Mention And Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	91,541		216,937
Commercial [Member] | Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	606,664		1,242,519
Owner Occupied Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	750,994	[1]
Owner Occupied Commercial [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	29,413	[1]
Owner Occupied Commercial [Member] | Accrual [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	54,344	[1]
Owner Occupied Commercial [Member] | Non Accrual [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	12,088	[1]
Owner Occupied Commercial [Member] | Doubtful/Nonaccrual [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	1,236	[1]
Owner Occupied Commercial [Member] | Special Mention And Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	97,081	[1]
Owner Occupied Commercial [Member] | Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	653,913	[1]
Commercial Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	604,556		622,799
Commercial Mortgages [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	30,722		50,044
Commercial Mortgages [Member] | Accrual [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	13,812		13,664
Commercial Mortgages [Member] | Non Accrual [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	5,243		15,814
Commercial Mortgages [Member] | Doubtful/Nonaccrual [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	632
Commercial Mortgages [Member] | Special Mention And Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	50,409		79,522
Commercial Mortgages [Member] | Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	554,147		543,277
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	114,177		106,154
Construction [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	429		9,747
Construction [Member] | Accrual [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	13,053		19,039
Construction [Member] | Non Accrual [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	2,121		22,124
Construction [Member] | Doubtful/Nonaccrual [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	499
Construction [Member] | Special Mention And Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	16,102		50,910
Construction [Member] | Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrual	$ 98,075		$ 55,244

[1] Prior to 2012, owner-occupied commercial loans were included in commercial loan balances.