Variable Interest Entities (Variable Interest Entity, Consolidated, Carrying Amount, Assets) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Assets	$ 33,753,752	$ 32,590,690
Liabilities	30,424,047	29,356,065
Other Assets [Member] | Tax Credit - Finance Investments | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	44,700	37,200
Accounts Payable and Accrued Liabilities [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Liabilities		10,200
Accounts Payable and Accrued Liabilities [Member] | Tax Credit - Finance Investments | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Liabilities	12,700
Other Investments [Member] | Other Non-Marketable Investments | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	44,700	34,300
Unfunded Loan Commitment [Member] | Other Non-Marketable Investments | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 78,200	$ 72,700