Loans and the Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Receivables [Abstract]
Non Accrual Contractual Due	90 days
Loans Pledged as Collateral	$ 2,800,000		$ 2,500,000
Loans performing under the restructured terms	21,300		21,400
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	30,600		30,600
Troubled debt restructurings	51,900		$ 52,000
Specific allowance	47	$ 0
Provision for loan losses associated with impacts of the COVID-19 pandemic	$ 13,500