Securities - Amortized Cost and Fair Value of Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Amortized Cost
Held to maturity, amortized cost, total	$ 493,467	$ 184,484
Fair Value
Held to maturity, fair value, total	489,289	192,179
Amortized Cost
Available for sale, amortized cost, total	1,310,406	1,371,539
Fair Value
Available for sale, fair value, total	1,322,776	1,398,157
Other Debt Obligations
Amortized Cost
Held to maturity, amortized cost, due in less than one year	0
Held to maturity, amortized cost, due after one year through five years	0
Held to maturity, amortized cost, due after five years through ten years	0
Held to maturity, amortized cost, due after ten years	0
Held to maturity, amortized cost, total	0
Fair Value
Held to maturity, fair value, due in less than one year	0
Held to maturity, fair value, due after one year through five years	0
Held to maturity, fair value, due after five years through ten years	0
Held to maturity, fair value, due after ten years	0
Held to maturity, fair value, total	0
Amortized Cost
Available for sale, amortized cost, due in less than one year	400
Available for sale, amortized cost, due after one year through five years	12,316
Available for sale, amortized cost, due after five years through ten years	8,505
Available for sale, amortized cost, due after ten years	18,479
Available for sale, amortized cost, total	39,700
Fair Value
Available for sale, fair value, due in less than one year	402
Available for sale, fair value, due after one year through five years	13,175
Available for sale, fair value, due after five years through ten years	8,923
Available for sale, fair value, due after ten years	19,675
Available for sale, fair value, total	42,175
Mortgage-backed securities and collateralized mortgage obligations of U.S. government-sponsored entities
Amortized Cost
Held to maturity, amortized cost, total	493,467
Fair Value
Held to maturity, fair value, total	489,289	192,179
Amortized Cost
Available for sale, amortized cost, total	987,402	1,038,437
Fair Value
Available for sale, fair value, total	995,720	1,060,654
Private mortgage-backed securities and collateralized mortgage obligations
Amortized Cost
Held to maturity, amortized cost, total	0
Fair Value
Held to maturity, fair value, total	0
Amortized Cost
Available for sale, amortized cost, total	73,469	89,284
Fair Value
Available for sale, fair value, total	75,189	91,205
Collateralized loan obligations
Amortized Cost
Held to maturity, amortized cost, total	0
Fair Value
Held to maturity, fair value, total	0
Amortized Cost
Available for sale, amortized cost, total	209,835	202,563
Fair Value
Available for sale, fair value, total	$ 209,692	$ 202,195