Securities (Amortized Cost and Fair Value of Debt Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Debt Securities Available for Sale, Due in one year or less, Amortized Cost	$ 72
Debt Securities Available for Sale, Due after one year through five years, Amortized Cost	1,024,989
Debt Securities Available for Sale, Due after five years through ten years, Amortized Cost	2,980,929
Debt Securities Available for Sale, Due after ten years, Amortized Cost	2,232,845
Securities Available for Sale, Gross Amortized Cost	6,238,835	$ 6,310,214
Debt Securities Available for Sale, Due in one year or less, Fair Value	72
Debt Securities Available for Sale, Due after one year through five years, Fair Value	979,364
Debt Securities Available for Sale, Due after five years through ten years, Fair Value	2,699,847
Debt Securities Available for Sale, Due after ten years, Fair Value	1,886,337
Total available for sale debt securities, Fair Value	5,565,620	5,556,041
Debt Securities Held to Maturity, Due in one year or less, Amortized Cost	11,637
Debt Securities Held to Maturity, Due after one year through five years, Amortized Cost	538,020
Debt Securities Held to Maturity, Due after five years through ten years, Amortized Cost	918,433
Debt Securities Held to Maturity, Due after ten years, Amortized Cost	1,356,974
Total held to maturity debt securities, Amortized Cost	2,825,064	2,852,495
Debt Securities Held to Maturity, Due in one year or less, Fair Value	11,573
Debt Securities Held to Maturity, Due after one year through five years, Fair Value	520,589
Debt Securities Held to Maturity, Due after five years through ten years, Fair Value	851,024
Debt Securities Held to Maturity, Due after ten years, Fair Value	1,240,574
Total held to maturity debt securities, Fair Value	$ 2,623,760	$ 2,615,398