Fair Value Measurements and Derivative Instruments (Available-for-sale Securities Maturities) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Amortized cost
Within 1 year	$ 39,047
After 1 year through 5 years	58,494
After 5 years through 10 years	69,077
After 10 years	68,638
Total	235,256	$ 270,313
Estimated fair value
Within 1 year	39,133
After 1 year through 5 years	59,246
After 5 years through 10 years	70,267
After 10 years	71,008
Total	$ 239,654	$ 265,329

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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