Consolidated Statements of Cash Flows - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2016	Nov. 30, 2015	Nov. 30, 2014
Operating Activities
Net income (loss)	$ 7.0	$ 18.0	$ (16.2)	$ (50.0)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Loss (income) from discontinued operations, net of income taxes	0.0	0.1	(0.9)	0.7
Depreciation and amortization	5.1	64.9	65.1	63.7
Amortization of debt discount and financing costs	0.2	2.3	2.7	3.6
Stock-based compensation	(0.4)	12.9	8.6	5.7
Retirement benefits, net	5.4	31.8	62.7	31.2
Loss on debt repurchased	0.0	34.4	1.9	60.6
Loss on bank amendment	0.0	0.1	0.0	0.2
Loss on disposal of long-lived assets	0.0	0.5	0.7	2.8
Gain on sale of technology	0.0	0.0	(1.0)	(6.8)
Tax benefit on stock-based awards	(2.4)	(0.3)	(2.5)	(1.3)
Changes in assets and liabilities, net of effects from acquisition:
Accounts receivable	2.0	33.1	(1.0)	28.9
Inventories	1.3	(28.9)	(19.5)	(32.0)
Other current assets, net	(4.8)	(22.6)	(25.7)	(7.1)
Real estate held for entitlement and leasing	(0.1)	(6.0)	(7.8)	(15.0)
Receivable from Northrop	(0.5)	1.2	6.1	(2.8)
Recoverable from the U.S. government and other third parties for environmental remediation costs	3.2	(33.8)	(127.8)	8.5
Other noncurrent assets	0.5	(7.8)	11.9	(24.1)
Accounts payable	(41.0)	27.0	(5.1)	(18.2)
Advance payments on contracts	27.2	(9.1)	6.3	96.9
Other current liabilities	5.6	(37.5)	(17.8)	19.8
Deferred income taxes	(7.1)	4.8	(27.6)	(7.1)
Reserves for environmental remediation costs	(3.8)	47.4	140.1	(5.3)
Other noncurrent liabilities and other	0.3	25.9	12.0	(0.2)
Net cash provided by (used in) continuing operations	(2.3)	158.4	65.2	152.7
Net cash used in discontinued operations	0.0	0.0	(0.1)	(2.1)
Net Cash Provided by (Used in) Operating Activities	(2.3)	158.4	65.1	150.6
Investing Activities
Purchase of Rocketdyne Business	0.0	0.0	0.0	0.2
Proceeds from sale of technology	0.0	0.5	1.0	7.5
Capital expenditures	(1.2)	(47.6)	(36.8)	(43.4)
Net Cash Used in Investing Activities	(1.2)	(47.1)	(35.8)	(35.7)
Financing Activities
Proceeds from issuance of debt	0.0	800.0	0.0	189.0
Debt issuance costs including equity component of convertible debt	0.0	(9.5)	0.0	(4.2)
Debt repayments/repurchases	(1.3)	(700.6)	(81.2)	(166.3)
Proceeds from shares issued under equity plans, net	0.0	4.2	1.3	0.2
Repurchase of shares for option cost and to satisfy tax withholding obligations	(0.2)	(3.9)	(6.7)	(2.1)
Purchase of treasury stock	0.0	0.0	0.0	(64.5)
Tax benefit on stock-based awards	2.4	0.3	2.5	1.3
Net Cash Provided by (Used in) Financing Activities	0.9	90.5	(84.1)	(46.6)
Net Increase (Decrease) in Cash and Cash Equivalents	(2.6)	201.8	(54.8)	68.3
Cash and Cash Equivalents at Beginning of Period	211.1	208.5	265.9	197.6
Cash and Cash Equivalents at End of Period	208.5	410.3	211.1	265.9
Supplemental disclosures of cash flow information
Cash paid for interest	2.7	39.0	49.3	46.9
Cash paid for income taxes, net	0.0	31.1	27.9	4.9
Conversion of debt to common stock	$ 0.0	$ 49.0	$ 49.0	$ 0.0