Divestitures and Acquisitions - Schedule of Major Classes of Assets and Liabilities Included as Discontinued Operations/Held For Sale (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Assets
Current assets		$ 547
Liabilities
Current liabilities		237
Discontinued Operations, Held-for-sale [Member]
Assets
Current assets	$ 664	1,262	$ 1,213
Liabilities
Current liabilities	220	230
MSI [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Assets
Cash and cash equivalents		61
Billed receivables, net of allowances of $6		77
Contracts in process		70
Inventories		70
Other current assets		10
Current assets		288
Goodwill		231
Other assets		28
Total assets of discontinued operations/held for sale		547
Liabilities
Accounts payable, trade		31
Accrued employment costs		22
Accrued expenses		33
Advance payments and billings in excess of costs incurred		55
Other current liabilities		21
Current liabilities		162
Pension and postretirement benefits		56
Other liabilities		19
Total liabilities of discontinued operations/held for sale		237
NSS [Member] | Discontinued Operations, Held-for-sale [Member]
Assets
Current assets	201	198
Property, plant and equipment, net	25	27
Goodwill	390	989
Other assets	48	48
Total assets of discontinued operations/held for sale	664	1,262
Liabilities
Accounts payable, trade	48	36
Other current liabilities	78	75
Current liabilities	126	111
Long-term liabilities	94	119
Total liabilities of discontinued operations/held for sale	$ 220	$ 230