Securities (Narrative) (Details)	6 Months Ended
	Jun. 30, 2022 USD ($) Security	Dec. 31, 2021 USD ($) Security
Debt and Equity Securities, FV-NI [Line Items]
Securities with an aggregate fair value	$ 5,602,830,000	$ 3,901,659,000
Securities available for sale, amortized cost	6,358,434,000	6,984,530,000
Securities classified as trading	0	$ 0
Allowance for credit loss	$ 0
Securities that met the criteria of a credit loss event | Security	0
Number of securities with market values below their cost basis | Security	671	142
Asset Pledged as Collateral without Right [Member]
Debt and Equity Securities, FV-NI [Line Items]
Securities pledged as collateral	$ 4,100,000,000	$ 4,000,000,000.0
Available for Sale and Held to Maturity [Member]
Debt and Equity Securities, FV-NI [Line Items]
Amortized cost of securities excluding accrued interest	27,200,000	$ 25,500,000
Securities with an aggregate fair value	561,800,000
Unrealized loss	15,400,000
Securities available for sale, amortized cost	$ 561,800,000