Investment Securities - Amortized Cost of Investment Securities Held to Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 2,325,311	$ 2,180,047
Aaa
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	156,735
Aa1
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	152,330
Aa2
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	174,021
Aa3
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	130,579
A1
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	105,264
A2
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	30,114
A3
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	10,110
Non-rated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1,566,158
State and municipal
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1,082,257	$ 1,057,301
State and municipal | Aaa
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	96,155
State and municipal | Aa1
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	152,330
State and municipal | Aa2
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	174,021
State and municipal | Aa3
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	130,579
State and municipal | A1
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	105,264
State and municipal | A2
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	30,114
State and municipal | A3
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	10,110
State and municipal | Non-rated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	383,684
Other
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1,243,054
Other | Aaa
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	60,580
Other | Aa1
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0
Other | Aa2
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0
Other | Aa3
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0
Other | A1
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0
Other | A2
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0
Other | A3
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0
Other | Non-rated
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 1,182,474