Securities (Amortized Cost and Fair Value of Debt Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Investments Debt And Equity Securities [Abstract]
Debt Securities Available for Sale, Due in one year or less, Amortized Cost	$ 2,387
Debt Securities Available for Sale, Due after one year through five years, Amortized Cost	669,087
Debt Securities Available for Sale, Due after five years through ten years, Amortized Cost	2,995,387
Debt Securities Available for Sale, Due after ten years, Amortized Cost	3,317,669
Securities Available for Sale, Gross Amortized Cost	6,984,530	$ 5,766,234
Debt Securities Available for Sale, Due in one year or less, Fair Value	2,403
Debt Securities Available for Sale, Due after one year through five years, Fair Value	696,513
Debt Securities Available for Sale, Due after five years through ten years, Fair Value	3,002,023
Debt Securities Available for Sale, Due after ten years, Fair Value	3,285,759
Total available for sale debt securities, Fair Value	6,986,698	5,999,327
Debt Securities Held to Maturity, Due in one year or less, Amortized Cost	11,225
Debt Securities Held to Maturity, Due after one year through five years, Amortized Cost	361,412
Debt Securities Held to Maturity, Due after five years through ten years, Amortized Cost	618,557
Debt Securities Held to Maturity, Due after ten years, Amortized Cost	574,557
Total held to maturity debt securities, Amortized Cost	1,565,751	1,357,170
Debt Securities Held to Maturity, Due in one year or less, Fair Value	11,311
Debt Securities Held to Maturity, Due after one year through five years, Fair Value	377,421
Debt Securities Held to Maturity, Due after five years through ten years, Fair Value	650,531
Debt Securities Held to Maturity, Due after ten years, Fair Value	592,219
Total held to maturity debt securities, Fair Value	$ 1,631,482	$ 1,467,581