Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Valuation of Financial Instruments Recorded on Fair Value Basis

The following table summarizes the valuation of our financial instruments recorded on a fair value basis as of December 31, 2017 and 2018:

	Fair value measurements
	Total		Quotedprices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
	(In millions)
Asset:
December 31, 2017 -
Noncurrent marketable securities    (See Note 6)	$	10.7	$	10.7	$	-	$	-
December 31, 2018 -
Noncurrent marketable securities    (See Note 6)	$	3.4	$	3.4	$	-	$	-

Financial Instruments not Carried at Fair Value but which Require Fair Value Disclosure

Other– The following table presents the financial instruments that are not carried at fair value but which require fair value disclosure as of December 31, 2017 and 2018.

		December 31, 2017				December 31, 2018
		Carrying amount		Fair value		Carrying amount		Fair value
	(In millions)
Cash, cash equivalents and restricted cash		$	323.7	$	323.7	$	374.7	$	374.7
Long-term debt - Fixed rate Senior Notes			471.1		495.1		452.4		412.9
Common stockholders' equity			754.3		2,986.8		839.8		1,335.3