Securities - Amortized Cost and Fair Value of Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Amortized Cost
Due within one year	$ 14,851
Due after one year through five years	38,030
Due after five years through ten years	78,289
Due after ten years	175,427
Amortized Cost	1,263,898	$ 1,276,871
Fair Value
Due within one year	14,938
Due after one year through five years	39,616
Due after five years through ten years	81,913
Due after ten years	175,207
Fair Value	1,303,494	1,290,613
Other debt securities
Amortized Cost
Debt securities, without fixed maturity, amortized cost	37,826
Amortized Cost	58,642	55,364
Fair Value
Debt securities, without fixed maturity, fair value	40,015
Fair Value	60,870	56,365
Government agency mortgage backed securities \| Residential mortgage backed securities:
Amortized Cost
Debt securities, without fixed maturity, amortized cost	659,279
Amortized Cost	659,279	708,970
Fair Value
Debt securities, without fixed maturity, fair value	684,165
Fair Value	684,165	716,105
Government agency mortgage backed securities \| Commercial mortgage backed securities:
Amortized Cost
Debt securities, without fixed maturity, amortized cost	32,706
Amortized Cost	32,706	30,372
Fair Value
Debt securities, without fixed maturity, fair value	34,417
Fair Value	34,417	31,007
Government agency collateralized mortgage obligations \| Residential mortgage backed securities:
Amortized Cost
Debt securities, without fixed maturity, amortized cost	137,181
Amortized Cost	137,181	172,178
Fair Value
Debt securities, without fixed maturity, fair value	139,520
Fair Value	139,520	173,238
Government agency collateralized mortgage obligations \| Commercial mortgage backed securities:
Amortized Cost
Debt securities, without fixed maturity, amortized cost	90,309
Amortized Cost	90,309	76,456
Fair Value
Debt securities, without fixed maturity, fair value	93,703
Fair Value	$ 93,703	$ 77,751

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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