Allowance for Loan Losses - Recorded Investment in Commercial Loan Classes by Internally Assigned Risk Ratings (Details) - Commercial - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 5,512,796	$ 4,672,445
% of Total	100.00%	100.00%
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 5,254,076	$ 4,402,167
% of Total	95.30%	94.30%
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 103,878	$ 87,344
% of Total	1.90%	1.80%
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 152,651	$ 181,192
% of Total	2.80%	3.90%
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 2,191	$ 1,742
% of Total	0.00%	0.00%
Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 3,416,518	$ 2,921,832
% of Total	100.00%	100.00%
Commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 3,270,437	$ 2,774,997
% of Total	95.70%	95.00%
Commercial real estate | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 57,285	$ 54,627
% of Total	1.70%	1.90%
Commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 86,772	$ 90,913
% of Total	2.50%	3.10%
Commercial real estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 2,023	$ 1,295
% of Total	0.00%	0.00%
Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 1,720,833	$ 1,493,416
% of Total	100.00%	100.00%
Commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 1,636,314	$ 1,394,067
% of Total	95.10%	93.40%
Commercial and industrial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 36,484	$ 25,368
% of Total	2.10%	1.70%
Commercial and industrial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 47,980	$ 73,621
% of Total	2.80%	4.90%
Commercial and industrial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 55	$ 360
% of Total	0.00%	0.00%
Commercial construction
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 375,445	$ 257,197
% of Total	100.00%	100.00%
Commercial construction | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 347,324	$ 233,103
% of Total	92.50%	90.70%
Commercial construction | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 10,109	$ 7,349
% of Total	2.70%	2.80%
Commercial construction | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 17,899	$ 16,658
% of Total	4.80%	6.50%
Commercial construction | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans recorded investment	$ 113	$ 87
% of Total	0.00%	0.00%