Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Change in Accounting Estimate

The following table presents the effect of aggregate net EAC adjustments:

	Year Ended December 31
$ in millions, except per share data	2020		2019		2018
Revenue	$	504	$	538	$	631
Operating income	466		480		577
Net earnings(1)	368		379		456
Diluted earnings per share(1)	2.20		2.23		2.61

(1)Based on a 21% federal statutory tax rate.

Contract with Customer, Asset and Liability

Net contract assets are as follows:

$ in millions	December 31, 2020		December 31, 2019		$ Change		% Change
Unbilled receivables, net	$	5,140	$	5,334	$	(194)	(4)	%
Advance payments and amounts in excess of costs incurred	(2,517)		(2,237)		(280)		13	%
Net contract assets	$	2,623	$	3,097	$	(474)	(15)	%

Property, Plant and Equipment

Major classes of property, plant and equipment and their useful lives are as follows:

		December 31
Useful life in years, $ in millions	Useful Life	2020		2019
Land and land improvements	Up to 40(1)	$	628	$	619
Buildings and improvements	Up to 45	2,762		2,575
Machinery and other equipment	Up to 20	7,206		6,997
Capitalized software costs	3-5	602		606
Leasehold improvements	Lease Term(2)	2,208		1,965
Property, plant and equipment, at cost		13,406		12,762
Accumulated depreciation		(6,335)		(5,850)
Property, plant and equipment, net		$	7,071	$	6,912

(1)Land is not a depreciable asset.

(2)Leasehold improvements are depreciated over the shorter of the useful life of the asset or lease term.

Accumulated Other Comprehensive Loss

The components of accumulated other comprehensive loss are as follows:

	December 31
$ in millions	2020		2019
Unamortized prior service credit, net of tax expense of $3 for 2020 and $17 for 2019	$	10	$	51
Cumulative translation adjustment and other, net	(138)		(148)
Total accumulated other comprehensive loss	$	(128)	$	(97)