Loans - Recorded Investment in Loan Classes Based on Payment Activity (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Non-PCI Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 4,122,662	$ 4,012,411
Non-PCI Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,447,974	2,485,239
Non-PCI Loans [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	400,303	410,875
Non-PCI Loans [Member] | Automobile Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,021,782	901,399
Non-PCI Loans [Member] | Other Consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	252,603	214,898
PCI Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	675,605	806,268
PCI Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	169,622	201,197
PCI Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	431,971	521,249
PCI Loans [Member] | Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	16,300	22,354
PCI Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	20,990	22,349
PCI Loans [Member] | Consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	36,722	39,119
Performing Loans [Member] | Non-PCI Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	4,101,366	3,990,427
Performing Loans [Member] | Non-PCI Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,428,784	2,465,290
Performing Loans [Member] | Non-PCI Loans [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	398,318	409,009
Performing Loans [Member] | Non-PCI Loans [Member] | Automobile Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,021,661	901,230
Performing Loans [Member] | Non-PCI Loans [Member] | Other Consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	252,603	214,898
Performing Loans [Member] | PCI Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	648,143	759,521
Performing Loans [Member] | PCI Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	156,369	185,185
Performing Loans [Member] | PCI Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	418,655	498,184
Performing Loans [Member] | PCI Loans [Member] | Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	16,300	16,791
Performing Loans [Member] | PCI Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	20,467	21,381
Performing Loans [Member] | PCI Loans [Member] | Consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	36,352	37,980
Non-Performing Loans [Member] | Non-PCI Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	21,296	21,984
Non-Performing Loans [Member] | Non-PCI Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	19,190	19,949
Non-Performing Loans [Member] | Non-PCI Loans [Member] | Home Equity [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,985	1,866
Non-Performing Loans [Member] | Non-PCI Loans [Member] | Automobile Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	121	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	27,462	46,747
Non-Performing Loans [Member] | PCI Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	13,253	16,012
Non-Performing Loans [Member] | PCI Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	13,316	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	523	968
Non-Performing Loans [Member] | PCI Loans [Member] | Consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 370	$ 1,139