Loans - Recorded Investment in Loan Classes Based on Payment Activity (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Non-PCI Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 4,191,088	$ 4,012,411
Non-PCI Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,423,044	2,485,239
Non-PCI Loans [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	401,072	410,875
Non-PCI Loans [Member] | Automobile Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,091,287	901,399
Non-PCI Loans [Member] | Other Consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	275,685	214,898
PCI Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	629,688	806,268
PCI Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	144,715	201,197
PCI Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	413,765	521,249
PCI Loans [Member] | Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	16,022	22,354
PCI Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	20,323	22,349
PCI Loans [Member] | Consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	34,863	39,119
Performing Loans [Member] | Non-PCI Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	4,171,403	3,990,427
Performing Loans [Member] | Non-PCI Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,405,739	2,465,290
Performing Loans [Member] | Non-PCI Loans [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	398,787	409,009
Performing Loans [Member] | Non-PCI Loans [Member] | Automobile Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,091,192	901,230
Performing Loans [Member] | Non-PCI Loans [Member] | Other Consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	275,685	214,898
Performing Loans [Member] | PCI Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	608,343	759,521
Performing Loans [Member] | PCI Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	133,842	185,185
Performing Loans [Member] | PCI Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	404,226	498,184
Performing Loans [Member] | PCI Loans [Member] | Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	16,022	16,791
Performing Loans [Member] | PCI Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	19,783	21,381
Performing Loans [Member] | PCI Loans [Member] | Consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	34,470	37,980
Non-Performing Loans [Member] | Non-PCI Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	19,685	21,984
Non-Performing Loans [Member] | Non-PCI Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	17,305	19,949
Non-Performing Loans [Member] | Non-PCI Loans [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,285	1,866
Non-Performing Loans [Member] | Non-PCI Loans [Member] | Automobile Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	95	169
Non-Performing Loans [Member] | Non-PCI Loans [Member] | Other Consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		0
Non-Performing Loans [Member] | PCI Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	21,345	46,747
Non-Performing Loans [Member] | PCI Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	10,873	16,012
Non-Performing Loans [Member] | PCI Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	9,539	23,065
Non-Performing Loans [Member] | PCI Loans [Member] | Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	0	5,563
Non-Performing Loans [Member] | PCI Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	540	968
Non-Performing Loans [Member] | PCI Loans [Member] | Consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 393	$ 1,139