MARKETABLE SECURITIES - Summary of Available-for-Sale Debt Securities (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Amortized Cost	$ 203.0	$ 190.0
Pre-Tax Unrealized Gains	8.9	0.4
Pre-Tax Unrealized Losses	(0.1)	(4.0)
Fair Value	$ 211.8	$ 186.4

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on 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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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on 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).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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