Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Jul. 01, 2021	Dec. 31, 2020
Assets
Cash and cash equivalents	$ 1,269.3	$ 1,873.3
Restricted Cash, Current	0.3	0.3
Accounts receivable, net	516.3	484.4
Unbilled Receivables, Current	358.7	368.4
Inventory, net	1,305.4	1,422.3
Other current assets	341.9	336.3
Total current assets	3,791.9	4,485.0
Property, plant and equipment, net	2,445.8	2,503.8
Operating Lease, Right-of-Use Asset	84.5	70.6
Unbilled Receivable, Non Current	0.0	4.4
Pension assets	477.2	455.9
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent	1.2	0.1
Goodwill	619.0	565.3
Intangible Assets, Net (Excluding Goodwill)	214.9	215.2
Deferred income taxes	106.6	83.6
Other assets	7,741.1	8,383.9
Liabilities, Current [Abstract]
Accounts Payable, Current	607.1	558.9
Accrued Liabilities, Current	333.6	365.6
Deferred Compensation Liability, Current	28.4	57.0
Long-term Debt and Lease Obligation, Current	47.9	340.7
Operating Lease, Liability, Current	7.7	5.5
Customer Advances, Current	85.0	18.9
Billings in Excess of Cost, Current	87.1	97.6
Provision for Loss on Contracts	231.4	184.6
Deferred Revenue, Current	18.1	22.2
Other Liabilities, Current	85.1	58.4
Liabilities Noncurrent
Long-term debt	3,552.7	3,532.9
Operating Lease, Liability, Noncurrent	78.8	66.6
Advance payments, long-term	255.1	327.4
Pension/OPEB obligation	415.2	440.2
Billings in Excess of Cost, Noncurrent	300.3	372.0
Provision for Loss on Contacts, Non Current	507.4	561.4
Deferred grant income liability - non-current	27.5	28.1
Deferred revenue and other deferred credits	36.0	38.9
Deferred income taxes	449.5	437.0
Deferred Tax Liabilities, Net, Noncurrent	26.9	13.0
Additional Paid in Capital [Abstract]
Additional paid-in capital	1,150.1	1,139.8
AccumulatedOtherComprehensiveIncomeLossNetOfTaxAbstract
Accumulated other comprehensive loss	(152.1)	(154.1)
Retained Earnings Accumulated Deficit [Abstract]
Retained earnings	$ 2,017.4	$ 2,326.4
Treasury Stock, Shares	41,523,470	41,523,470
Treasury Stock, Value	$ (2,456.7)	$ (2,456.7)
Total stockholders' equity	559.8	856.5
Noncontrolling interest	0.5	0.5
Total equity	560.3	857.0
Total liabilities and equity	7,741.1	8,383.9
Liabilities, Current	1,531.4	1,709.4
Class A [Member]
Stockholders' Equity Attributable to Parent [Abstract]
Common stock	$ 1.1	$ 1.1
Retained Earnings Accumulated Deficit [Abstract]
Common Stock, Shares Authorized	200,000,000	200,000,000
Class B [Member]
Retained Earnings Accumulated Deficit [Abstract]
Common Stock, Shares Authorized	150,000,000	150,000,000