Adoption of New Standard (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 27, 2018	Sep. 28, 2017	Sep. 27, 2018	Sep. 28, 2017	Dec. 31, 2017	Dec. 31, 2016
Item Effected [Line Items]
Cash and cash equivalents	$ 683.4	$ 726.6	$ 683.4	$ 726.6	$ 423.3	$ 697.7
Restricted Cash and Cash Equivalents	0.3	3.2	0.3	3.2	2.2	0.0
Accounts Receivable, Net, Current	685.1		685.1		722.2
Unbilled Receivables, Current	513.2		513.2		0.0
Inventory, net	931.0		931.0		1,449.9
Other Assets, Current	35.4		35.4		53.5
Unbilled Receivable, Non Current	53.5		53.5		0.0
Assets, Current	2,848.4		2,848.4		2,651.1
Property, Plant and Equipment, Net	2,123.0		2,123.0		2,105.3
Assets for Plan Benefits, Defined Benefit Plan	372.3		372.3		347.1
Revenues	1,813.7	1,748.2	5,386.7	5,268.4
Cost of Goods and Services Sold	1,543.1	1,486.6	4,601.3	4,762.8
Selling, General and Administrative Expense	37.3	49.8	154.5	149.9
Unusual or Infrequent Item, or Both, Net of Insurance Proceeds	0.0	0.0	0.0	19.9
Research and Development Expense	10.8	9.5	31.3	21.2
Interest and Debt Expense	24.2	10.4	60.3	30.1
Other Nonoperating Income (Expense)	7.4	11.0	(0.8)	32.2
Income Tax Expense (Benefit)	(36.9)	(55.9)	(99.7)	(84.9)
Net Income (Loss) Attributable to Parent	$ 168.8	$ 147.2	$ 439.4	$ 232.1
Earnings Per Share, Basic	$ 1.61	$ 1.27	$ 4.02	$ 1.97
Earnings Per Share, Diluted	$ 1.59	$ 1.26	$ 3.98	$ 1.95
Other Assets, Noncurrent	$ 284.9		$ 284.9		164.3
Assets	5,682.1		5,682.1		5,267.8
Accounts Payable, Current	882.4		882.4		693.1
Accrued Liabilities, Current	354.0		354.0		269.3
Billings in Excess of Cost, Current	153.5		153.5		0.0
Provision for Loss on Contracts	147.3		147.3		0.0
Deferred Compensation Liability, Current	42.0		42.0		109.5
Long-term Debt and Capital Lease Obligations, Current	25.0		25.0		31.1
Customer Advances, Current	112.7		112.7		100.0
Deferred Revenue, Current	7.1		7.1		64.6
Deferred Grant Income Liability Current	19.4		19.4		21.6
Other Liabilities, Current	68.8		68.8		331.8
Billings in Excess of Cost, Noncurrent	353.8		353.8		0.0
Provision for Loss on Contacts, Non Current	72.6		72.6		0.0
Liabilities, Current	1,812.2		1,812.2		1,621.0
Long-term Debt and Capital Lease Obligations	1,869.7		1,869.7		1,119.9
Customer Advances, Noncurrent	146.4		146.4		231.7
Liability, Defined Benefit Plan, Noncurrent	38.4		38.4		40.8
Deferred Revenue and Credits, Noncurrent	26.8		26.8		161.0
Deferred Grant Income Liability Noncurrent	30.7		30.7		39.3
Other Liabilities, Noncurrent	215.1		215.1		252.6
Preferred Stock, Value, Issued	0.0		0.0		0.0
Additional Paid in Capital, Common Stock	983.4		983.4		1,086.9
Accumulated Other Comprehensive Income (Loss), Net of Tax	(145.0)		(145.0)		(128.5)
Retained Earnings (Accumulated Deficit)	2,548.7		2,548.7		2,422.4
Treasury Stock, Value	2,272.3		2,272.3		1,580.9
Stockholders' Equity Attributable to Parent	1,115.9		1,115.9		1,801.0
Stockholders' Equity Attributable to Noncontrolling Interest	0.5		0.5		0.5
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	1,116.4		1,116.4		1,801.5
Liabilities and Equity	5,682.1		5,682.1		5,267.8
Restricted Cash and Investments, Noncurrent	20.2	$ 20.0	20.2	$ 20.0	20.0	19.9
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	703.9	749.8	703.9	749.8	$ 445.5	$ 717.6
Transition Adjustment	277.0		277.0
Transition Adjustment - deferred production costs	640.3		640.3
Transition adjustment - forward loss reserves	364.0		364.0
Transition Adjustment - contract asset	342.0		342.0
Transition Adjustment - contract liability	113.0		113.0
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Item Effected [Line Items]
Accounts Receivable, Net, Current	131.0		131.0
Unbilled Receivables, Current	(513.2)		(513.2)
Inventory, net	445.2		445.2
Other Assets, Current	36.1		36.1
Unbilled Receivable, Non Current	(53.5)		(53.5)
Revenues	15.9		106.6
Cost of Goods and Services Sold	68.2		207.7
Income Tax Expense (Benefit)	10.6		20.9
Net Income (Loss) Attributable to Parent	$ (41.7)		$ (80.2)
Earnings Per Share, Basic	$ (0.40)		$ (0.73)
Earnings Per Share, Diluted	$ (0.39)		$ (0.72)
Other Assets, Noncurrent	$ (78.5)		$ (78.5)
Assets	(32.9)		(32.9)
Accrued Liabilities, Current	(7.1)		(7.1)
Billings in Excess of Cost, Current	(153.5)		(153.5)
Provision for Loss on Contracts	(147.3)		(147.3)
Deferred Revenue, Current	144.9		144.9
Other Liabilities, Current	290.8		290.8
Billings in Excess of Cost, Noncurrent	(353.8)		(353.8)
Provision for Loss on Contacts, Non Current	(72.6)		(72.6)
Deferred Revenue and Credits, Noncurrent	71.5		71.5
Accumulated Other Comprehensive Income (Loss), Net of Tax	(2.2)		(2.2)
Retained Earnings (Accumulated Deficit)	196.4		196.4
Liabilities and Equity	(32.9)		(32.9)
Accounting Standards Update 2014-09 [Member]
Item Effected [Line Items]
Accounts Receivable, Net, Current	816.1		816.1
Unbilled Receivables, Current	0.0		0.0
Inventory, net	1,376.2		1,376.2
Other Assets, Current	71.5		71.5
Unbilled Receivable, Non Current	0.0		0.0
Revenues	1,829.6		5,493.3
Cost of Goods and Services Sold	1,611.3		4,809.0
Income Tax Expense (Benefit)	(26.3)		(78.8)
Net Income (Loss) Attributable to Parent	$ 127.1		$ 359.2
Earnings Per Share, Basic	$ 1.21		$ 3.29
Earnings Per Share, Diluted	$ 1.20		$ 3.26
Other Assets, Noncurrent	$ 206.4		$ 206.4
Assets	5,649.2		5,649.2
Accrued Liabilities, Current	346.9		346.9
Billings in Excess of Cost, Current	0.0		0.0
Provision for Loss on Contracts	0.0		0.0
Deferred Revenue, Current	152.0		152.0
Other Liabilities, Current	359.6		359.6
Billings in Excess of Cost, Noncurrent	0.0		0.0
Provision for Loss on Contacts, Non Current	0.0		0.0
Deferred Revenue and Credits, Noncurrent	98.3		98.3
Accumulated Other Comprehensive Income (Loss), Net of Tax	(147.2)		(147.2)
Retained Earnings (Accumulated Deficit)	2,745.1		2,745.1
Liabilities and Equity	$ 5,649.2		$ 5,649.2
Balance prior to Adoption of ASU 2017-07 [Member]
Item Effected [Line Items]
Cost of Goods and Services Sold		1,478.5		4,738.3
Selling, General and Administrative Expense		48.8		146.8
Other Nonoperating Income (Expense)		1.9		4.6
Impact of 2017-07 [Member]
Item Effected [Line Items]
Cost of Goods and Services Sold		8.1		24.5
Selling, General and Administrative Expense		1.0		3.1
Other Nonoperating Income (Expense)		$ 9.1		$ 27.6