Debt Securities Available for Sale - Expected Maturities of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Amortized Cost
Amortized Cost	$ 1,132,936	$ 1,086,143
Fair Value
Fair Value	1,177,925	1,098,336
Debt Securities excluding Mortgage-based securities and CMOs
Amortized Cost
One year or less	22,397
More than one year to five years	37,414
More than five years to ten years	59,575
More than ten years	471
Amortized Cost	119,857
Fair Value
One year or less	22,464
More than one year to five years	39,410
More than five years to ten years	59,338
More than ten years	485
Fair Value	121,697
Mortgage-backed securities and collateralized mortgage obligations
Amortized Cost
Amortized Cost	1,013,079	968,165
Fair Value
Fair Value	$ 1,056,228	$ 979,881

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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