Loans - Recorded Investment Based on Payment Activity (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Non-PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 6,352,767	$ 6,220,351
Non-PCI Loans | Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	3,694,463	3,682,984
Non-PCI Loans | Consumer | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	385,987	371,340
Non-PCI Loans | Consumer | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,362,143	1,319,206
Non-PCI Loans | Consumer | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	910,174	846,821
Non-PCI Loans | Performing Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	6,338,699	6,204,779
Non-PCI Loans | Performing Loans | Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	3,682,394	3,670,067
Non-PCI Loans | Performing Loans | Consumer | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	384,357	369,184
Non-PCI Loans | Performing Loans | Consumer | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,361,995	1,319,126
Non-PCI Loans | Performing Loans | Consumer | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	909,953	846,402
Non-PCI Loans | Non-Performing Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	14,068	15,572
Non-PCI Loans | Non-Performing Loans | Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	12,069	12,917
Non-PCI Loans | Non-Performing Loans | Consumer | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	1,630	2,156
Non-PCI Loans | Non-Performing Loans | Consumer | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	148	80
Non-PCI Loans | Non-Performing Loans | Consumer | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	221	419
PCI Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	3,771,957	4,190,086
PCI Loans | Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	377,987	428,416
PCI Loans | Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	128,658	160,263
PCI Loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	696,871	740,657
PCI Loans | Commercial real estate | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,327,890	2,494,966
PCI Loans | Commercial real estate | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	240,551	365,784
PCI Loans | Performing Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	3,716,872	4,133,961
PCI Loans | Performing Loans | Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	372,531	421,609
PCI Loans | Performing Loans | Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	126,234	158,502
PCI Loans | Performing Loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	668,887	710,045
PCI Loans | Performing Loans | Commercial real estate | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,309,294	2,478,990
PCI Loans | Performing Loans | Commercial real estate | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	239,926	364,815
PCI Loans | Non-Performing Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	55,085	56,125
PCI Loans | Non-Performing Loans | Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	5,456	6,807
PCI Loans | Non-Performing Loans | Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,424	1,761
PCI Loans | Non-Performing Loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	27,984	30,612
PCI Loans | Non-Performing Loans | Commercial real estate | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	18,596	15,976
PCI Loans | Non-Performing Loans | Commercial real estate | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 625	$ 969