Debt Securities Available for Sale - Expected Maturities of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Amortized Cost
Amortized Cost	$ 1,095,282	$ 1,049,932
Fair Value
Fair Value	1,090,177	1,032,868
Debt Securities excluding Mortgage-based securities and CMOs
Amortized Cost
One year or less	95
More than one year to five years	60,043
More than five years to ten years	59,166
More than ten years	5,000
Amortized Cost	124,304
Fair Value
One year or less	95
More than one year to five years	59,857
More than five years to ten years	58,616
More than ten years	4,480
Fair Value	123,048
Mortgage-backed securities and collateralized mortgage obligations
Amortized Cost
Amortized Cost	970,978	934,631
Fair Value
Fair Value	$ 967,129	$ 920,007

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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-Publisher FASB
-Name Accounting Standards Codification
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