Securities (Amortized Cost and Fair Value of Debt Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Debt Securities Available for Sale, Due in one year or less, Amortized cost	$ 106,858
Debt Securities Available for Sale, Due after one year through five years, Amortized cost	585,990
Debt Securities Available for Sale, Due after five years through ten years, Amortized cost	2,549,295
Debt Securities Available for Sale, Due after ten years, Amortized cost	2,293,069
Securities Available for Sale, Gross Amortized cost	5,535,212	$ 5,496,718
Debt Securities Available for Sale, Due in one year or less, Fair value	105,620
Debt Securities Available for Sale, Due after one year through five years, Fair value	566,852
Debt Securities Available for Sale, Due after five years through ten years, Fair value	2,287,101
Debt Securities Available for Sale, Due after ten years, Fair value	1,945,850
Total available for sale debt securities, Fair value	4,905,423	4,915,195
Debt Securities Held to Maturity, Due in one year or less, Amortized cost	92,336
Debt Securities Held to Maturity, Due after one year through five years, Amortized cost	734,660
Debt Securities Held to Maturity, Due after five years through ten years, Amortized cost	716,536
Debt Securities Held to Maturity, Due after ten years, Amortized cost	1,110,227
Total held to maturity debt securities, Amortized cost	2,653,759	2,684,779
Debt Securities Held to Maturity, Due in one year or less, Fair value	91,307
Debt Securities Held to Maturity, Due after one year through five years, Fair value	696,030
Debt Securities Held to Maturity, Due after five years through ten years, Fair value	666,275
Debt Securities Held to Maturity, Due after ten years, Fair value	982,998
Total held to maturity debt securities, Fair value	$ 2,436,610	$ 2,485,918