Securities - Amortized Cost and Fair Value of Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Amortized Cost
Due within one year	$ 22,688
Due after one year through five years	36,561
Due after five years through ten years	74,683
Due after ten years	59,237
Amortized Cost	1,254,258	$ 1,264,529
Fair Value
Due within one year	22,867
Due after one year through five years	37,425
Due after five years through ten years	77,266
Due after ten years	58,731
Fair Value	1,268,280	1,250,777
Other debt securities
Amortized Cost
Debt securities, without fixed maturity, amortized cost	38,377
Amortized Cost	47,651	44,046
Fair Value
Debt securities, without fixed maturity, fair value	39,713
Fair Value	49,080	43,927
Government agency mortgage backed securities \| Residential mortgage backed securities
Amortized Cost
Debt securities, without fixed maturity, amortized cost	600,257
Amortized Cost	600,257	621,690
Fair Value
Debt securities, without fixed maturity, fair value	606,453
Fair Value	606,453	613,283
Government agency mortgage backed securities \| Commercial mortgage-backed securities
Amortized Cost
Debt securities, without fixed maturity, amortized cost	31,795
Amortized Cost	31,795	21,957
Fair Value
Debt securities, without fixed maturity, fair value	32,545
Fair Value	32,545	21,830
Government agency collateralized mortgage obligations \| Residential mortgage backed securities
Amortized Cost
Debt securities, without fixed maturity, amortized cost	319,896
Amortized Cost	319,896	332,697
Fair Value
Debt securities, without fixed maturity, fair value	321,211
Fair Value	321,211	326,989
Government agency collateralized mortgage obligations \| Commercial mortgage-backed securities
Amortized Cost
Debt securities, without fixed maturity, amortized cost	70,764
Amortized Cost	70,764	28,446
Fair Value
Debt securities, without fixed maturity, fair value	72,069
Fair Value	$ 72,069	$ 28,335

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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