Allowance for Credit Losses - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing receivable, collectively evaluated for impairment	$ 5,979,260	$ 5,110,068
Financing receivable, allowance for credit losses, collectively evaluated for impairment	69,769	39,651
Financing receivable, individually evaluated for impairment and acquired with deteriorated credit quality	42,000
Financing receivable, allowance for credit losses, individually evaluated for impairment and acquired with deteriorated credit quality	1,300
Accrued interest receivable on loans	16,100
Financing receivable, allowance for credit loss	$ 71,124	$ 40,003	$ 37,688
Financing receivable, allowance for credit loss, percentage of total loans	1.18%	0.78%
Debt securities, accrued interest after allowance for credit loss	$ 3,300
Cumulated adjustment for adoption of ASU
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing receivable, allowance for credit loss		$ 6,656	$ 0