Loans - Recorded Investment in Loan Classes Based on Payment Activity (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Non-PCI Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 3,833,226	$ 3,850,453
Non-PCI Loans [Member] | Residential mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,397,884	2,445,627
Non-PCI Loans [Member] | Home equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	415,501	438,881
Non-PCI Loans [Member] | Automobile loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	835,271	786,528
Non-PCI Loans [Member] | Other consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	184,570	179,417
PCI Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	951,405	1,167,664
PCI Loans [Member] | Residential mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	24,004	26,461
PCI Loans [Member] | Commercial and industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	220,576	298,600
PCI Loans [Member] | Commercial real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	639,384	765,893
PCI Loans [Member] | Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	25,836	27,513
PCI Loans [Member] | Consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	41,605	49,197
Performing Loans [Member] | Non-PCI Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	3,804,623	3,814,499
Performing Loans [Member] | Non-PCI Loans [Member] | Residential mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,371,830	2,413,004
Performing Loans [Member] | Non-PCI Loans [Member] | Home equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	413,173	436,483
Performing Loans [Member] | Non-PCI Loans [Member] | Automobile loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	835,050	786,223
Performing Loans [Member] | Non-PCI Loans [Member] | Other consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	184,570	178,789
Performing Loans [Member] | PCI Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	888,991	1,095,804
Performing Loans [Member] | PCI Loans [Member] | Residential mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	20,111	22,173
Performing Loans [Member] | PCI Loans [Member] | Commercial and industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	216,501	292,163
Performing Loans [Member] | PCI Loans [Member] | Commercial real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	594,919	715,812
Performing Loans [Member] | PCI Loans [Member] | Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	17,150	17,967
Performing Loans [Member] | PCI Loans [Member] | Consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	40,310	47,689
Non-Performing Loans [Member] | Non-PCI Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	28,603	35,954
Non-Performing Loans [Member] | Non-PCI Loans [Member] | Residential mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	26,054	32,623
Non-Performing Loans [Member] | Non-PCI Loans [Member] | Home equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,328	2,398
Non-Performing Loans [Member] | Non-PCI Loans [Member] | Automobile loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	221	305
Non-Performing Loans [Member] | Non-PCI Loans [Member] | Other consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		628
Non-Performing Loans [Member] | PCI Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	62,414	71,860
Non-Performing Loans [Member] | PCI Loans [Member] | Residential mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	3,893	4,288
Non-Performing Loans [Member] | PCI Loans [Member] | Commercial and industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	4,075	6,437
Non-Performing Loans [Member] | PCI Loans [Member] | Commercial real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	44,465	50,081
Non-Performing Loans [Member] | PCI Loans [Member] | Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	8,686	9,546
Non-Performing Loans [Member] | PCI Loans [Member] | Consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 1,295	$ 1,508