Fair Value Measurements - Contractual Maturities of Available for Sale Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Maturing in one year or less	$ 876	$ 1,645
Maturing in second year through fifth year	16,071	24,649
Maturing in sixth year through tenth year	38,801	14,769
Maturing after ten years	34,963	35,299
Total debt securities	$ 90,711	$ 76,362	$ 73,221

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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