Loans - Recorded Investment Based on Payment Activity (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Non-PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 4,687,151	$ 4,768,989
PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,654,701	1,771,502
Performing Loans | Non-PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	4,674,106	4,755,740
Performing Loans | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,628,844	1,744,491
Non-Performing Loans | Non-PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	13,045	13,249
Non-Performing Loans | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	25,857	27,011
Commercial and industrial | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	244,165	281,177
Commercial and industrial | Performing Loans | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	235,700	272,483
Commercial and industrial | Non-Performing Loans | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	8,465	8,694
Commercial real estate loans | PCI Loans | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,065,189	1,091,339
Commercial real estate loans | PCI Loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	77,591	114,680
Commercial real estate loans | Performing Loans | PCI Loans | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,054,623	1,080,376
Commercial real estate loans | Performing Loans | PCI Loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	76,496	113,370
Commercial real estate loans | Non-Performing Loans | PCI Loans | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	10,566	10,963
Commercial real estate loans | Non-Performing Loans | PCI Loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,095	1,310
Residential mortgage | Non-PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,574,346	2,684,195
Residential mortgage | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	171,101	183,723
Residential mortgage | Performing Loans | Non-PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,562,696	2,672,120
Residential mortgage | Performing Loans | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	167,510	179,793
Residential mortgage | Non-Performing Loans | Non-PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	11,650	12,075
Residential mortgage | Non-Performing Loans | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	3,591	3,930
Consumer | Non-PCI Loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	369,232	376,213
Consumer | Non-PCI Loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,149,918	1,139,082
Consumer | Non-PCI Loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	593,655	569,499
Consumer | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	96,655	100,583
Consumer | Performing Loans | Non-PCI Loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	367,947	375,185
Consumer | Performing Loans | Non-PCI Loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,149,808	1,138,936
Consumer | Performing Loans | Non-PCI Loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	593,655	569,499
Consumer | Performing Loans | PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	94,515	98,469
Consumer | Non-Performing Loans | Non-PCI Loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,285	1,028
Consumer | Non-Performing Loans | Non-PCI Loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	110	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	$ 2,140	$ 2,114