Recorded Investment in PCI Loans by Class Based on Individual Loan Payment Activity (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	$ 11,423,852	$ 9,799,641
Residential Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	2,727,114	2,285,590
PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	1,340,987	271,844
PCI Loans | Commercial and Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	346,257	83,742
PCI Loans | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	857,441	160,651
PCI Loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	50,008	6,974
PCI Loans | Residential Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	32,789	15,546
PCI Loans | Consumer Portfolio Segment
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	54,492	4,931
Performing Financing Receivable | Residential Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	2,695,069	2,253,944
Performing Financing Receivable | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	1,254,588	195,143
Performing Financing Receivable | PCI Loans | Commercial and Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	336,106	67,424
Performing Financing Receivable | PCI Loans | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	801,365	112,047
Performing Financing Receivable | PCI Loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	37,172	623
Performing Financing Receivable | PCI Loans | Residential Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	26,965	10,118
Performing Financing Receivable | PCI Loans | Consumer Portfolio Segment
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	52,980	4,931
Nonperforming Financing Receivable | Residential Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	32,045	31,646
Nonperforming Financing Receivable | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	86,397	76,701
Nonperforming Financing Receivable | PCI Loans | Commercial and Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	10,150	16,318
Nonperforming Financing Receivable | PCI Loans | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	56,076	48,604
Nonperforming Financing Receivable | PCI Loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	12,836	6,351
Nonperforming Financing Receivable | PCI Loans | Residential Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	5,823	5,428
Nonperforming Financing Receivable | PCI Loans | Consumer Portfolio Segment
Financing Receivable, Credit Quality Indicator [Line Items]
Commercial and industrial	$ 1,512