Investments - Investments Classified by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Amortized Cost And Estimated Fair Value Of Investment Securities Available For Sale By Contractual Maturity [Line Items]
Maturing within one year, Amortized Cost	$ 7,057	$ 7,726
Maturing after one year through five years, Amortized Cost	183,343	199,840
Maturing after five years through ten years, Amortized Cost	56,211	47,802
Maturing after ten years, Amortized Cost	87,011	83,606
Amortized Cost, Total	566,930	569,942
Maturing within one year, Fair Value	7,103	7,789
Maturing after one year through five years, Fair Value	180,783	195,519
Maturing after five years through ten years, Fair Value	56,502	47,661
Maturing after ten years, Fair Value	88,317	83,444
Fair Value, Total	563,628	560,479
U.S. Government Agencies Collateralized by Mortgage Obligations [Member]
Amortized Cost And Estimated Fair Value Of Investment Securities Available For Sale By Contractual Maturity [Line Items]
Investment securities not due at a single maturity date, Amortized Cost	233,308	230,968
Investment securities not due at a single maturity date, Fair Value	$ 230,923	$ 226,066

Amortized cost and estimated fair value of investment securities available for sale by contractual maturity.

No definition available.

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- Definition

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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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth fiscal year through tenth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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- Definition

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Fair value of investment in debt security, measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing after tenth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Amortized cost of investment in debt security measured at fair value with change recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), maturing in next fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), without single maturity date and not allocated over maturity grouping.

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