Loans - Risk Category of Commercial Loans Before Adoption of CECL (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	$ 5,140,940
Total Commercial Loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	4,356,696
Commercial, secured by real estate
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	3,589,593
Commercial, industrial and other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	431,934
Construction
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	335,169
1 | Total Commercial Loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	898
1 | Commercial, secured by real estate
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	0
1 | Commercial, industrial and other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	898
1 | Construction
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	0
2 | Total Commercial Loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	17,988
2 | Commercial, secured by real estate
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	0
2 | Commercial, industrial and other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	17,988
2 | Construction
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	0
3 | Total Commercial Loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	113,184
3 | Commercial, secured by real estate
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	74,072
3 | Commercial, industrial and other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	39,112
3 | Construction
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	0
4 | Total Commercial Loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	1,091,142
4 | Commercial, secured by real estate
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	965,825
4 | Commercial, industrial and other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	107,376
4 | Construction
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	17,941
5 | Total Commercial Loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	2,856,662
5 | Commercial, secured by real estate
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	2,332,863
5 | Commercial, industrial and other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	215,975
5 | Construction
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	307,824
5W - Watch | Total Commercial Loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	137,498
5W - Watch | Commercial, secured by real estate
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	100,347
5W - Watch | Commercial, industrial and other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	30,192
5W - Watch | Construction
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	6,959
6 - Other assets especially mentioned | Total Commercial Loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	66,766
6 - Other assets especially mentioned | Commercial, secured by real estate
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	55,438
6 - Other assets especially mentioned | Commercial, industrial and other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	11,328
6 - Other assets especially mentioned | Construction
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	0
7 - Substandard | Total Commercial Loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	72,558
7 - Substandard | Commercial, secured by real estate
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	61,048
7 - Substandard | Commercial, industrial and other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	9,065
7 - Substandard | Construction
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, before allowance for credit loss and fee	$ 2,445