Allowance for Credit Losses - Recorded Investment in Commercial Loan Classes by Internally Assigned Risk Ratings (Details) - Commercial $ in Thousands	Dec. 31, 2019 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 5,512,796
Total percentage of recorded investment in commercial loan	100.00%
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 5,254,076
Total percentage of recorded investment in commercial loan	95.30%
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 103,878
Total percentage of recorded investment in commercial loan	1.90%
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 152,651
Total percentage of recorded investment in commercial loan	2.80%
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 2,191
Total percentage of recorded investment in commercial loan	0.00%
Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 3,416,518
Total percentage of recorded investment in commercial loan	100.00%
Commercial real estate | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 3,270,437
Total percentage of recorded investment in commercial loan	95.70%
Commercial real estate | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 57,285
Total percentage of recorded investment in commercial loan	1.70%
Commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 86,772
Total percentage of recorded investment in commercial loan	2.50%
Commercial real estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 2,023
Total percentage of recorded investment in commercial loan	0.00%
Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 1,720,833
Total percentage of recorded investment in commercial loan	100.00%
Commercial and industrial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 1,636,314
Total percentage of recorded investment in commercial loan	93.40%
Commercial and industrial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 36,484
Total percentage of recorded investment in commercial loan	1.70%
Commercial and industrial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 47,980
Total percentage of recorded investment in commercial loan	4.90%
Commercial and industrial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 55
Total percentage of recorded investment in commercial loan	0.00%
Commercial construction
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 375,445
Total percentage of recorded investment in commercial loan	100.00%
Commercial construction | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 347,324
Total percentage of recorded investment in commercial loan	92.50%
Commercial construction | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 10,109
Total percentage of recorded investment in commercial loan	2.70%
Commercial construction | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 17,899
Total percentage of recorded investment in commercial loan	4.80%
Commercial construction | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases receivables, recorded investment	$ 133
Total percentage of recorded investment in commercial loan	0.00%