MARKETABLE SECURITIES - Contractual Maturities of Available-for-Sale Debt Securities (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Amortized Cost
Less than one year	$ 26.9
One to five years	48.8
Six to ten years	38.4
Greater than ten years	90.2
Amortized Cost	204.3	$ 190.0
Fair Value
Less than one year	26.9
One to five years	49.6
Six to ten years	40.0
Greater than ten years	93.1
Fair Value	$ 209.6	$ 186.4

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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