Short-Term Borrowings (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) item	Dec. 31, 2020 USD ($)
Short-term Debt [Line Items]
Short-term borrowings	$ 1,665,061	$ 1,667,513
FHLB Borrowings [Member]
Short-term Debt [Line Items]
Short-term borrowings	$ 1,100,000	$ 1,100,000
FHLB Borrowings [Member] | FHLB Borrowings, 5 Fixed Rate Notes [Member] | Fixed-rate Term Notes [Member]
Short-term Debt [Line Items]
Number of fixed rate short-term borrowings | item	5
FHLB Borrowings [Member] | FHLB Borrowings, 5 Fixed Rate Notes [Member] | Fixed-rate Term Notes [Member] | Minimum [Member]
Short-term Debt [Line Items]
Short-term maturity year	2034
FHLB Borrowings [Member] | FHLB Borrowings, 5 Fixed Rate Notes [Member] | Fixed-rate Term Notes [Member] | Maximum [Member]
Short-term Debt [Line Items]
Short-term maturity year	2035