Derivatives (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) contracts	Dec. 31, 2019 USD ($) contracts	Dec. 31, 2018 USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Counterparty default losses on forward contracts	$ 0	$ 0	$ 0
Credit Derivatives [Line Items]
Commitments and contingent liabilities
Termination value of derivatives in net liability position	370	7,000
Required collateral posting	92,600	86,200
Variation Margin Payment	(330,500)	(144,800)
Derivative Credit Risk Valuation Adjustment, Change In Derivative Assets	$ (18,500)	$ (9,100)
Interest rate swaps
Credit Derivatives [Line Items]
Number of interest rate derivatives held | contracts	886	846
Notional amount of credit risk derivatives	$ 6,200,000	$ 5,700,000
Commitments To Originate Loans Held For Sale
Credit Derivatives [Line Items]
Commitments and contingent liabilities	821,073
Forward Sales Commitments
Credit Derivatives [Line Items]
Commitments and contingent liabilities	$ 1,003,221