Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Allowances and Reserve Balance	$ 22,000	$ 24,000
Expense Related to Qualified Affordable Housing Projects	19,000	17,000	$ 8,000
Remaining Investment in Qualified Affordable Housing Projects	234,000	132,000
Unfunded Equity Contributions Obligation Amount	123,000	51,000
Loans repurchased under make whole requests	$ 2,000	$ 2,000
Loans Sold To Outside Investors Loss Reimbursement Settlement Paid	negligible	negligible
Loans sold to outside investors original amount	$ 12,500,000
Loans sold to outside investors remaining outstanding amount	7,400,000
Residential mortgage loans sold with recourse risk	39,000	$ 47,000
Residential mortgage loans sold with credit recourse risk	45,000	57,000
Community Reinvestment, Obtaining Tax Credits, and Other Tax Benefits [Member]
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Carrying value of investments	248,000	136,000
Tax Credit and Other Investments
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Carrying value of investments	26,000	25,000
Mortgage Repurchase Reserve
Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities (Textuals) [Line Items]
Allowances and Reserve Balance	$ 795	$ 752