Short-Term Borrowings (Short-Term Borrowings) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Short-term Debt [Line Items]
Amount outstanding at period end	$ 1,665,061	$ 1,667,513
Federal Funds Purchased [Member]
Short-term Debt [Line Items]
Amount outstanding at period end	1,850	300
Average amount outstanding during period	3,762	9,708
Maximum amount at any month end during period	$ 4,400	$ 330,330
Weighted-average interest at period end	0.15%	0.15%
Weighted-average interest rate during period	0.43%	1.15%
Securities Sold Under Agreements to Repurchase [Member]
Short-term Debt [Line Items]
Amount outstanding at period end	$ 563,211	$ 567,213
Average amount outstanding during period	559,410	600,167
Maximum amount at any month end during period	$ 643,403	$ 806,645
Weighted-average interest at period end	0.05%	0.14%
Weighted-average interest rate during period	0.10%	0.24%
FHLB Borrowings [Member]
Short-term Debt [Line Items]
Amount outstanding at period end	$ 1,100,000	$ 1,100,000
Average amount outstanding during period	1,100,000	1,368,320
Maximum amount at any month end during period	$ 1,100,000	$ 2,110,000
Weighted-average interest at period end	0.49%	0.49%
Weighted-average interest rate during period	0.49%	0.62%