Securities (Schedule of Information Regarding Securities with Unrealized Losses) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Securities in an Unrealized Loss Position for Less than 12 Months
Fair Value, AFS and HTM	$ 1,269,291	$ 555,070
Unrealized Losses, AFS and HTM	26,854	2,348
Securities in an Unrealized Loss Position for More than 12 Months
Fair Value, AFS and HTM	10,634	7,003
Unrealized Losses, AFS and HTM	365	332
Total
Fair Value, AFS and HTM	1,279,925	562,073
Unrealized Losses, AFS and HTM	27,219	2,680
Government-sponsored enterprise securities
Securities in an Unrealized Loss Position for Less than 12 Months
Fair Value, AFS	67,022	29,812
Unrealized Losses, AFS	2,993	181
Securities in an Unrealized Loss Position for More than 12 Months
Fair Value, AFS	0	0
Unrealized Losses, AFS	0	0
Total
Fair Value, AFS	67,022	29,812
Unrealized Losses, AFS	2,993	181
Mortgage-backed securities
Securities in an Unrealized Loss Position for Less than 12 Months
Fair Value, AFS and HTM	1,094,263	497,992
Unrealized Losses, AFS and HTM	19,010	1,957
Securities in an Unrealized Loss Position for More than 12 Months
Fair Value, AFS and HTM	5,844	6,168
Unrealized Losses, AFS and HTM	155	167
Total
Fair Value, AFS and HTM	1,100,107	504,160
Unrealized Losses, AFS and HTM	19,165	2,124
Corporate bonds
Securities in an Unrealized Loss Position for Less than 12 Months
Fair Value, AFS	0	3,956
Unrealized Losses, AFS	0	45
Securities in an Unrealized Loss Position for More than 12 Months
Fair Value, AFS	4,790	835
Unrealized Losses, AFS	210	165
Total
Fair Value, AFS	4,790	4,791
Unrealized Losses, AFS	210	210
State and local governments
Securities in an Unrealized Loss Position for Less than 12 Months
Fair Value, HTM	108,006	23,310
Unrealized Losses, HTM	4,851	165
Securities in an Unrealized Loss Position for More than 12 Months
Fair Value, HTM	0	0
Unrealized Losses, HTM	0	0
Total
Fair Value, HTM	108,006	23,310
Unrealized Losses, HTM	$ 4,851	$ 165