Securities - Amortized Cost and Fair Value of Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Amortized Cost
Held to maturity, amortized cost, total	$ 227,092	$ 261,369
Fair Value
Held to maturity, fair value, total	235,946	262,213
Amortized Cost
Available for sale, amortized cost, total	953,342	940,765
Fair Value
Available for sale, fair value, total	976,025	946,855
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	2,100
Available for sale, amortized cost, due after one year through five years	8,655
Available for sale, amortized cost, due after five years through ten years	8,577
Available for sale, amortized cost, due after ten years	17,468
Available for sale, amortized cost, total	36,800
Fair Value
Available for sale, fair value, due in less than one year	2,125
Available for sale, fair value, due after one year through five years	9,063
Available for sale, fair value, due after five years through ten years	9,200
Available for sale, fair value, due after ten years	18,784
Available for sale, fair value, total	39,172
Mortgage-backed securities and collateralized mortgage obligations of U.S. government-sponsored entities
Amortized Cost
Held to maturity, amortized cost, total	227,092
Fair Value
Held to maturity, fair value, total	235,946	262,213
Amortized Cost
Available for sale, amortized cost, total	636,528	604,934
Fair Value
Available for sale, fair value, total	661,185	609,207
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	75,756	56,005
Fair Value
Available for sale, fair value, total	76,851	57,561
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	204,258	239,364
Fair Value
Available for sale, fair value, total	$ 198,817	$ 238,218