Investment Securities - Available-for-sale Securities with Unrealized Loss (Details) $ in Thousands	Mar. 31, 2022 USD ($) securities	Dec. 31, 2021 USD ($) securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	$ 984,808	$ 826,981
Less than 12 months, unrealized loss	$ 63,216	$ 13,838
Less than 12 months, Number of securities | securities	362	225
12 months or more, fair value	$ 153,275	$ 87,688
12 months or more, unrealized loss	$ 19,088	$ 3,894
12 months or more, Number of securities | securities	48	27
Total fair value	$ 1,138,083	$ 914,669
Total unrealized loss	82,304	17,732
U.S. Treasury and government agencies
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	107,070	16,914
Less than 12 months, unrealized loss	$ 1,926	$ 17
Less than 12 months, Number of securities | securities	24	6
12 months or more, fair value	$ 0	$ 0
12 months or more, unrealized loss	$ 0	$ 0
12 months or more, Number of securities | securities	0	0
Total fair value	$ 107,070	$ 16,914
Total unrealized loss	1,926	17
U.S. government sponsored agencies
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	71,303	72,406
Less than 12 months, unrealized loss	$ 5,610	$ 1,192
Less than 12 months, Number of securities | securities	18	13
12 months or more, fair value	$ 7,343	$ 4,854
12 months or more, unrealized loss	$ 967	$ 146
12 months or more, Number of securities | securities	2	1
Total fair value	$ 78,646	$ 77,260
Total unrealized loss	6,577	1,338
States and political subdivisions
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	129,520	101,397
Less than 12 months, unrealized loss	$ 11,628	$ 2,075
Less than 12 months, Number of securities | securities	102	71
12 months or more, fair value	$ 48,104	$ 30,853
12 months or more, unrealized loss	$ 7,120	$ 1,301
12 months or more, Number of securities | securities	19	11
Total fair value	$ 177,624	$ 132,250
Total unrealized loss	18,748	3,376
Residential mortgage-backed securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	632,616	573,139
Less than 12 months, unrealized loss	$ 40,240	$ 9,051
Less than 12 months, Number of securities | securities	198	113
12 months or more, fair value	$ 79,024	$ 51,103
12 months or more, unrealized loss	$ 8,613	$ 2,325
12 months or more, Number of securities | securities	20	14
Total fair value	$ 711,640	$ 624,242
Total unrealized loss	48,853	11,376
Commercial mortgage-backed securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	39,447	60,134
Less than 12 months, unrealized loss	$ 3,665	$ 1,494
Less than 12 months, Number of securities | securities	18	21
12 months or more, fair value	$ 17,882	$ 0
12 months or more, unrealized loss	$ 2,310	$ 0
12 months or more, Number of securities | securities	6	0
Total fair value	$ 57,329	$ 60,134
Total unrealized loss	5,975	1,494
Bank-issued trust preferred securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	4,852	2,991
Less than 12 months, unrealized loss	$ 147	$ 9
Less than 12 months, Number of securities | securities	2	1
12 months or more, fair value	$ 922	$ 878
12 months or more, unrealized loss	$ 78	$ 122
12 months or more, Number of securities | securities	1	1
Total fair value	$ 5,774	$ 3,869
Total unrealized loss	$ 225	$ 131