Securities (Available-for-sale Securities, Debt Maturities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Amortized Cost
Due in 1 year or less	$ 12,121
Due in 1 to 5 years	28,111
Due in 5 to 10 years	76,299
Due after 10 years	597,386
Total debt securities	713,917
Mortgage and asset-backed securities	2,579,081
Equity securities with a readily determinable fair value	18,435	$ 17,086
Total investment securities	3,311,433
Estimated Fair Value
Due in 1 year or less	12,171
Due in 1 to 5 years	28,434
Due in 5 to 10 years	77,942
Due after 10 years	598,536
Total debt securities	717,083
Mortgage and asset-backed securities	2,577,278
Equity securities with a readily determinable fair value	18,435	$ 17,086
Total investment securities	$ 3,312,796