Investment Securities - Held-to-Maturity with Unrecognized Losses (Details) $ in Thousands	Mar. 31, 2022 USD ($)
Fair Value
Less than 12 months	$ 1,722,864
12 months or longer	221,574
Total	1,944,438
Unrecognized Losses
Less than 12 months	(107,834)
12 months or longer	(18,854)
Total	(126,688)
U.S. government-sponsored entities and agencies
Fair Value
Less than 12 months	339,590
12 months or longer	140,819
Total	480,409
Unrecognized Losses
Less than 12 months	(35,610)
12 months or longer	(12,506)
Total	(48,116)
Mortgage-backed securities
Fair Value
Less than 12 months	394,393
12 months or longer	46,660
Total	441,053
Unrecognized Losses
Less than 12 months	(19,522)
12 months or longer	(2,535)
Total	(22,057)
States and political subdivisions
Fair Value
Less than 12 months	988,881
12 months or longer	34,095
Total	1,022,976
Unrecognized Losses
Less than 12 months	(52,702)
12 months or longer	(3,813)
Total	$ (56,515)