Investment Securities - Amortized Cost of Investment Securities Held to Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	$ 1,721,659	$ 1,227,668
Aaa
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	115,430
Aa1
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	131,246
Aa2
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	136,008
Aa3
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	96,915
A1
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	66,549
A2
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	18,962
A3
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	1,065
Baa2
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	527
Non-rated
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	1,154,957
State and municipal
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	863,426	$ 619,927
State and municipal | Aaa
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	54,753
State and municipal | Aa1
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	131,246
State and municipal | Aa2
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	136,008
State and municipal | Aa3
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	96,915
State and municipal | A1
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	66,549
State and municipal | A2
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	18,962
State and municipal | A3
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	1,065
State and municipal | Baa2
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	527
State and municipal | Non-rated
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	357,401
Other
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	858,233
Other | Aaa
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	60,677
Other | Aa1
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	0
Other | Aa2
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	0
Other | Aa3
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	0
Other | A1
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	0
Other | A2
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	0
Other | A3
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	0
Other | Baa2
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	0
Other | Non-rated
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost of investment securities held to maturity	$ 797,556