Balance Sheet Accounts (Tables)

3 Months Ended

Mar. 31, 2022

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Fair Value of Financial Instruments

			Fair value measurement as of March 31, 2022
	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Other Observable Inputs (Level 2)		Unobservable Inputs (Level 3)
	(In millions)
Money market funds	$	360.5	$	360.5	$	—	$	—
Registered investment companies	1.2		1.2		—		—
Commercial paper	139.9		—		139.9		—
Equity securities	10.1		10.1		—		—
Total	$	511.7	$	371.8	$	139.9	$	—

			Fair value measurement as of December 31, 2021
	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Other Observable Inputs (Level 2)		Unobservable Inputs (Level 3)
	(In millions)
Money market funds	$	388.6	$	388.6	$	—	$	—
Registered investment companies	1.3		1.3		—		—
Commercial paper	35.0		—		35.0		—
Equity securities	10.6		10.6		—		—
Total	$	435.5	$	400.5	$	35.0	$	—

Schedule of Estimated Fair Value and Principal Amount of Outstanding Debt

The following table summarizes the estimated fair value and principal amount for outstanding debt obligations excluding finance lease obligations:

	Fair Value				Principal Amount
	March 31, 2022		December 31, 2021		March 31, 2022		December 31, 2021
	(In millions)
Term loan	$	269.8	$	275.8	$	275.6	$	282.2
21/4% Notes	229.9		266.1		145.9		145.9
Total	$	499.7	$	541.9	$	421.5	$	428.1

Schedule of Accounts Receivable

Accounts Receivable

	March 31, 2022		December 31, 2021
	(In millions)
Billed receivables under long-term contracts	$	143.2	$	60.3
Other trade receivables	0.2		0.3
Accounts receivable	$	143.4	$	60.6

Schedule of Other Current Assets

Other Current Assets

	March 31, 2022		December 31, 2021
	(In millions)
Deferred costs recoverable from the U.S. government	$	40.4	$	37.4
Income tax receivable	—		13.8
Inventories	11.1		10.0
Prepaid expenses	15.5		15.3
Other	26.6		23.0
Other current assets	$	93.6	$	99.5

Schedule of Property, Plant and Equipment, net

Property, Plant and Equipment, net

	March 31, 2022		December 31, 2021
	(In millions)
Land	$	71.1	$	71.1
Buildings and improvements	505.1		503.0
Machinery and equipment, including capitalized software	501.6		499.1
Construction-in-progress	48.8		50.0
	1,126.6		1,123.2
Less: accumulated depreciation	(713.3)		(702.1)
Property, plant and equipment, net	$	413.3	$	421.1

Schedule of Other Noncurrent Assets

Other Noncurrent Assets

	March 31, 2022		December 31, 2021
	(In millions)
Real estate held for entitlement and leasing	$	103.8	$	103.7
Deferred costs recoverable from the U.S. government	62.2		62.1
Receivable from Northrop Grumman Corporation for environmental remediation costs	33.0		34.5
Other	37.3		43.0
Other noncurrent assets	$	236.3	$	243.3

Schedule of Other Current Liabilities

Other Current Liabilities

	March 31, 2022		December 31, 2021
	(In millions)
Accrued compensation and employee benefits	$	103.5	$	122.0
Income taxes payable	42.7		—
Other	66.9		50.7
Other current liabilities	$	213.1	$	172.7