Internal Risk Rating Categories for Commercial Portfolio (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	$ 6,119,185	$ 4,874,718
Commercial and Industrial [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	1,395,036	1,093,629
Commercial Real Estate [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	4,002,359	3,251,248
Construction Loans [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	547,293	365,165
Small Business [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	174,497	164,676
Pass [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	5,848,531	4,695,094
Pass [Member] | Commercial and Industrial [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	1,274,155	1,014,370
Pass [Member] | Commercial Real Estate [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	3,860,555	3,156,989
Pass [Member] | Construction Loans [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	542,608	361,884
Pass [Member] | Small Business [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	171,213	161,851
Potential weakness [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	164,416	74,886
Potential weakness [Member] | Commercial and Industrial [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	63,485	16,860
Potential weakness [Member] | Commercial Real Estate [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	97,268	56,840
Potential weakness [Member] | Construction Loans [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	2,247	298
Potential weakness [Member] | Small Business [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	1,416	888
Definite weakness [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	106,238	101,248
Definite weakness [Member] | Commercial and Industrial [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	57,396	58,909
Definite weakness [Member] | Commercial Real Estate [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	44,536	37,419
Definite weakness [Member] | Construction Loans [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	2,438	2,983
Definite weakness [Member] | Small Business [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	1,868	1,937
Parital loss probable [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	0	3,490
Parital loss probable [Member] | Commercial and Industrial [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	0	3,490
Parital loss probable [Member] | Commercial Real Estate [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	0	0
Parital loss probable [Member] | Construction Loans [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	0	0
Parital loss probable [Member] | Small Business [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	0	0
Definite loss [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	0	0
Definite loss [Member] | Commercial and Industrial [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	0	0
Definite loss [Member] | Commercial Real Estate [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	0	0
Definite loss [Member] | Construction Loans [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	0	0
Definite loss [Member] | Small Business [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	$ 0	$ 0