Balance Sheet Accounts and Supplemental Disclosures (Tables)

12 Months Ended

Dec. 31, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Accounts Receivable

	As of December 31,
	2020		2019
	(In millions)
Billed	$	75.3	$	122.9
Reserve on billed trade receivables	—		(10.6)
Other trade receivables	0.3		0.2
Accounts receivable, net	$	75.6	$	112.5

Schedule of Other Current Assets, net

	As of December 31,
	2020		2019
	(In millions)
Deferred costs recoverable from the U.S. government	$	41.0	$	47.1
Income tax receivable	46.9		43.4
Prepaid expenses	18.0		13.9
Inventories	10.0		24.0
Other	20.6		17.4
Other current assets, net	$	136.5	$	145.8

Schedule of Property, Plant and Equipment, net

	As of December 31,
	2020		2019
	(In millions)
Land	$	71.2	$	71.2
Buildings and improvements	433.4		434.9
Machinery and equipment, including capitalized software	471.3		488.2
Construction-in-progress	105.5		70.2
	1,081.4		1,064.5
Less: accumulated depreciation	(658.3)		(654.6)
Property, plant and equipment, net	$	423.1	$	409.9

Schedule of Intangible Assets

	As of December 31, 2020
	Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount
	(In millions)
Customer related	$	87.2	$	75.3	$	11.9
Intellectual property\trade secrets	34.2		19.7		14.5
Trade name	21.0		5.4		15.6
Acquired technology	19.2		16.4		2.8
Intangible assets	$	161.6	$	116.8	$	44.8

	As of December 31, 2019
	Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount
	(In millions)
Customer related	$	87.2	$	65.9	$	21.3
Intellectual property\trade secrets	34.2		17.1		17.1
Trade name	21.0		4.6		16.4
Acquired technology	19.2		15.8		3.4
Intangible assets	$	161.6	$	103.4	$	58.2

Schedule of Future Amortization Expense for Intangible Assets

Future amortization expense for the five succeeding years is estimated to be as follows:

Year Ending December 31,	Future Amortization Expense
	(In millions)
2021	$	9.9
2022	6.6
2023	6.1
2024	4.8
2025	3.7
	$	31.1

Schedule of Other Noncurrent Assets, net

	As of December 31,
	2020		2019
	(In millions)
Real estate held for entitlement and leasing	$	101.8	$	100.3
Receivable from Northrop Grumman Corporation for environmental remediation costs	40.5		46.5
Deferred costs recoverable from the U.S. government	54.7		54.8
Other	57.8		54.0
Other noncurrent assets, net	$	254.8	$	255.6

Schedule of Other Current Liabilities

	As of December 31,
	2020		2019
	(In millions)
Accrued compensation and employee benefits	$	118.0	$	103.1
Other	43.9		52.4
Other current liabilities	$	161.9	$	155.5

Schedule of Accumulated Other Comprehensive Loss, Net of Income Taxes

The following table presents the changes in accumulated other comprehensive loss by components, net of income taxes:

	Actuarial Losses, Net		Prior Service Credits (Costs), Net		Total
	(In millions)
December 31, 2018	$	(239.4)	$	—	$	(239.4)
Actuarial losses, net of income taxes	(26.5)		—		(26.5)
Amortization of net actuarial losses and prior service credits, net of income taxes	29.5		(0.1)		29.4
December 31, 2019	(236.4)		(0.1)		(236.5)
Actuarial losses, net of income taxes	(31.5)		—		(31.5)
Amortization of net actuarial losses and prior service costs, net of income taxes	40.3		0.1		40.4
December 31, 2020	$	(227.6)	$	—	$	(227.6)