Commitments, Off-Balance Sheet Arrangements, Legal Proceedings and Regulatory Matters (Details Textuals) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2020		Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Expense Related to Qualified Affordable Housing Projects	$ 6,000		$ 5,000
Remaining Investment in Qualified Affordable Housing Projects	268,000			$ 234,000
Variable Interest Entity Reporting Entity Involvement Unfunded Obligation Amount	148,000			123,000
Qualified Affordable Housing Investments, Impairment Loss	0			0
Loans Repurchased Under Make Whole Requests	$ 2,000			$ 2,000
Loans Sold To Outside Investors Loss ReimbursementSettlement Paid	no			negligible
Loans Sold To Outside Investors Original Amount	$ 12,700,000
Loans Sold To Outside Investors Remaining Outstanding Amount	7,400,000
Unfunded Commitments	56,276	[1]		$ 21,907
Residential Mortgage Loans Sold With Recourse Risk	44,000			39,000
Residential Mortgage Loans Sold With Credit Recourse Risk	42,000			45,000
SEC Schedule, 12-09, Reserve, Off-balance Sheet Activity [Member]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Provision for unfunded commitments	16,000			(2,500)
Unfunded Commitments				21,907	$ 24,336
Mortgage Repurchase Reserve
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Unfunded Commitments	1,000			795
UnconsolidatedProjectsLowIncomeHousing [Member]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Other Investments	282,000			248,000
PrincipalInvestmentCommitment [Member]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Other Investments	28,000			$ 26,000
Accounting Standards Update 2016-13 | SEC Schedule, 12-09, Reserve, Off-balance Sheet Activity [Member]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Cumulative effect of ASU 2016-13 adoption (CECL)	$ 18,690

[1] (b) At January 1, 2020, the adoption of ASU 2016-13 resulted in an increase to the allowance for loan losses of $112 million and an increase to the allowance for unfunded commitments of $19 million for a total increase to the ACLL of $131 million. A corresponding after tax decrease to common equity of $98 million was recorded along with a deferred tax asset of $33 million, included in accrued expenses and other liabilities. Prior periods were unadjusted due to the modified retrospective application of ASU 2016-13.