Fair Value Measurements and Derivative Instruments (Available-for-sale Securities Maturities) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Amortized cost
Within 1 year	$ 47,535
After 1 year through 5 years	68,901
After 5 years through 10 years	34,951
After 10 years	70,126
Total	221,513	$ 270,313
Estimated fair value
Within 1 year	47,589
After 1 year through 5 years	69,407
After 5 years through 10 years	36,121
After 10 years	71,012
Total	$ 224,129	$ 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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