Loans - Recorded Investment Based on Payment Activity (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Non-PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 4,724,936	$ 4,768,989
PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,541,469	1,771,502
Performing Loans | Non-PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	4,710,702	4,755,740
Performing Loans | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,507,754	1,744,491
Non-Performing Loans | Non-PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	14,234	13,249
Non-Performing Loans | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	33,715	27,011
Commercial and industrial | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	213,388	281,177
Commercial and industrial | Performing Loans | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	201,297	272,483
Commercial and industrial | Non-Performing Loans | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	12,091	8,694
Commercial Real Estate | PCI Loans | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,029,279	1,091,339
Commercial Real Estate | PCI Loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	55,877	114,680
Commercial Real Estate | Performing Loans | PCI Loans | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,014,923	1,080,376
Commercial Real Estate | Performing Loans | PCI Loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	54,775	113,370
Commercial Real Estate | Non-Performing Loans | PCI Loans | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	14,356	10,963
Commercial Real Estate | Non-Performing Loans | PCI Loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,102	1,310
Residential mortgage | Non-PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,569,500	2,684,195
Residential mortgage | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	155,277	183,723
Residential mortgage | Performing Loans | Non-PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,556,675	2,672,120
Residential mortgage | Performing Loans | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	150,031	179,793
Residential mortgage | Non-Performing Loans | Non-PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	12,825	12,075
Residential mortgage | Non-Performing Loans | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	5,246	3,930
Consumer | Non-PCI Loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	369,372	376,213
Consumer | Non-PCI Loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,150,217	1,139,082
Consumer | Non-PCI Loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	635,847	569,499
Consumer | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	87,648	100,583
Consumer | Performing Loans | Non-PCI Loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	368,066	375,185
Consumer | Performing Loans | Non-PCI Loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,150,114	1,138,936
Consumer | Performing Loans | Non-PCI Loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	635,847	569,499
Consumer | Performing Loans | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	86,728	98,469
Consumer | Non-Performing Loans | Non-PCI Loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,306	1,028
Consumer | Non-Performing Loans | Non-PCI Loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	103	146
Consumer | Non-Performing Loans | Non-PCI Loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	0	0
Consumer | Non-Performing Loans | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 920	$ 2,114