Internal Risk Rating Categories for Commercial Portfolio (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	$ 6,119,185
Commercial and Industrial [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	1,395,036
Commercial Real Estate [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	4,002,359
Construction Loans [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	547,293
Small Business [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	174,497
Pass [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	5,848,531
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
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
Pass [Member] | Construction Loans [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	542,608
Pass [Member] | Small Business [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	171,213
Potential weakness [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	164,416
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
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
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
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
Definite weakness [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	106,238
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
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
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
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
Parital loss probable [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	0
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
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
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
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
Definite loss [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	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
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
Definite loss [Member] | Construction Loans [Member]
Internal risk-rating categories for the Company's commercial portfolio
Financing Receivable, after Allowance for Credit Loss	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