Securities (Amortized Cost and Fair Value of Debt Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Debt Securities Available for Sale, Due in one year or less, Amortized cost	$ 2,667
Debt Securities Available for Sale, Due after one year through five years, Amortized cost	1,007,425
Debt Securities Available for Sale, Due after five years through ten years, Amortized cost	3,021,049
Debt Securities Available for Sale, Due after ten years, Amortized cost	2,120,042
Securities Available for Sale, Gross Amortized cost	6,151,183	$ 6,310,214
Debt Securities Available for Sale, Due in one year or less, Fair value	2,607
Debt Securities Available for Sale, Due after one year through five years, Fair value	951,597
Debt Securities Available for Sale, Due after five years through ten years, Fair value	2,693,028
Debt Securities Available for Sale, Due after ten years, Fair value	1,767,457
Total available for sale debt securities, Fair value	5,414,689	5,556,041
Debt Securities Held to Maturity, Due in one year or less, Amortized cost	6,636
Debt Securities Held to Maturity, Due after one year through five years, Amortized cost	665,030
Debt Securities Held to Maturity, Due after five years through ten years, Amortized cost	836,716
Debt Securities Held to Maturity, Due after ten years, Amortized cost	1,272,608
Total held to maturity debt securities, Amortized cost	2,780,990	2,852,495
Debt Securities Held to Maturity, Due in one year or less, Fair value	6,478
Debt Securities Held to Maturity, Due after one year through five years, Fair value	629,029
Debt Securities Held to Maturity, Due after five years through ten years, Fair value	768,352
Debt Securities Held to Maturity, Due after ten years, Fair value	1,136,397
Total held to maturity debt securities, Fair value	$ 2,540,256	$ 2,615,398