Accounting Changes and Error Corrections (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 26, 2019	Jun. 27, 2019	Mar. 28, 2019	Dec. 31, 2018	Sep. 27, 2018	Jun. 28, 2018	Mar. 29, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019	Dec. 31, 2016
Item Effected [Line Items]
Cash and cash equivalents	$ 2,350,500,000				$ 773,600,000				$ 2,350,500,000	$ 773,600,000	$ 423,300,000		$ 697,700,000
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	2,367,200,000				794,100,000				2,367,200,000	794,100,000	445,500,000		717,700,000
Restricted Cash, Current	300,000				300,000				300,000	300,000	2,200,000		0
Accounts Receivable, after Allowance for Credit Loss, Current	546,400,000				545,100,000				546,400,000	545,100,000
Revenues	1,959,300,000	$ 1,919,900,000	$ 2,016,100,000	$ 1,967,800,000	1,835,300,000	$ 1,813,700,000	$ 1,836,900,000	$ 1,736,100,000	7,863,100,000	7,222,000,000.0	6,983,000,000.0
Cost of Goods and Services Sold									6,786,400,000	6,135,900,000	6,195,300,000
Income Tax Expense (Benefit)									(132,800,000)	(139,800,000)	(180,000,000.0)
Net income	$ 67,700,000	$ 131,300,000	$ 168,000,000.0	$ 163,100,000	$ 177,600,000	$ 168,800,000	$ 145,200,000	$ 125,400,000	$ 530,100,000	$ 617,000,000.0	$ 354,900,000
Earnings Per Share, Basic	$ 0.65	$ 1.27	$ 1.62	$ 1.57	$ 1.70	$ 1.61	$ 1.32	$ 1.11	$ 5.11	$ 5.71	$ 3.04
Earnings Per Share, Diluted	$ 0.65	$ 1.26	$ 1.61	$ 1.55	$ 1.68	$ 1.59	$ 1.31	$ 1.10	$ 5.06	$ 5.65	$ 3.01
Unbilled Receivables, Current	$ 528,300,000				$ 469,400,000				$ 528,300,000	$ 469,400,000
Inventory, net	1,118,800,000				1,012,600,000				1,118,800,000	1,012,600,000
Other Assets, Current	98,700,000				48,300,000				98,700,000	48,300,000
Unbilled Receivable, Non Current	6,400,000				54,100,000				6,400,000	54,100,000
Other Assets, Noncurrent	80,400,000				83,200,000				80,400,000	83,200,000
Assets	7,606,000,000.0				5,685,900,000				7,606,000,000.0	5,685,900,000
Accrued Liabilities, Current	240,200,000				313,100,000				240,200,000	313,100,000
Billings in Excess of Cost, Current	158,300,000				157,900,000				158,300,000	157,900,000
Provision for Loss on Contracts	83,900,000				12,400,000				83,900,000	12,400,000
Deferred Revenue, Current	14,800,000				20,000,000.0				14,800,000	20,000,000.0
Other Liabilities, Current	39,300,000				58,200,000				39,300,000	58,200,000
Billings in Excess of Cost, Noncurrent	356,300,000				369,800,000				356,300,000	369,800,000
Provision for Loss on Contacts, Non Current	163,500,000				170,600,000				163,500,000	170,600,000
Deferred Revenue and Credits, Noncurrent	34,400,000				31,200,000				34,400,000	31,200,000
Retained Earnings (Accumulated Deficit)	3,201,300,000				2,713,200,000				3,201,300,000	2,713,200,000
Liabilities and Equity	7,606,000,000.0				5,685,900,000				7,606,000,000.0	5,685,900,000
Selling, General and Administrative Expense									261,400,000	210,400,000	$ 204,700,000
Other Nonoperating Income (Expense)									(5,800,000)	(7,000,000.0)	44,400,000
Restricted Cash and Investments, Noncurrent	$ 16,400,000				$ 20,200,000				$ 16,400,000	$ 20,200,000	$ 20,000,000.0		$ 20,000,000.0
Accounting Standards Update 2016-02 [Member]
Item Effected [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption												$ 52.7
Accounting Standards Update 2018-02 [Member]
Item Effected [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption				$ 8.3