Financial Instruments

12 Months Ended

Dec. 31, 2018

Investments, All Other Investments [Abstract]

Financial Instruments

Financial Instruments

At December 31, 2018 and 2017, the Company’s financial instruments consisted primarily of cash and cash equivalents, billed receivables, trade accounts payable, senior notes and foreign currency forward contracts. The carrying amounts of cash and cash equivalents, billed receivables and trade accounts payable are representative of their respective fair values because of the short-term maturities or expected settlement dates of these instruments. The carrying amounts and estimated fair values of the Company’s other financial instruments are presented in the table below.

	December 31, 2018						December 31, 2017
	Carrying Amount			Estimated Fair Value			Carrying Amount		Estimated Fair Value
	(in millions)
Senior notes(1)	$	3,321		$	3,355		$	3,330	$	3,502
Foreign currency forward contracts(2)	$	(16	)	$	(16	)	$	10	$	10

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⁽¹⁾  The Company measures the fair value of its senior notes using Level 2 inputs based primarily on current market yields for its existing debt traded in the secondary market.

⁽²⁾  The Company measures the fair values of foreign currency forward contracts based on forward exchange rates. See Note 15 for additional disclosures regarding the notional amounts and fair values of foreign currency forward contracts.