Revenue Recognition - Cumulative Effect of Revenue Recognition Accounting Change (Detail) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2018		Sep. 30, 2017	Sep. 30, 2018		Sep. 30, 2017	Dec. 31, 2017
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	[1]	$ 2,289		$ 959	$ 4,632		$ 2,267
Cost of operations		1,986		774	3,948		1,853
Income tax benefit		44		19	(19)		53
Net income		2		$ 95	84		$ 153
Current assets:
Contracts in progress		723	[2]		723	[2]		$ 621
Current liabilities:
Advance billings on contracts		1,733	[2]		1,733	[2]		32
Income taxes payable		143			143			35
Stockholders' equity:
Retained earnings		56	[3]		56	[3]		$ (48)
ASU 606 [Member] | Recognition Under Previous Guidance [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Revenues					4,873
Cost of operations					4,148
Income tax benefit					(18)
Net income					124
Current assets:
Contracts in progress		737			737
Current liabilities:
Advance billings on contracts		1,733			1,733
Income taxes payable		144			144
Stockholders' equity:
Retained earnings	[3]	69			69
ASU 606 [Member] | Adjustment [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Revenues					(241)
Cost of operations					(200)
Income tax benefit					(1)
Net income					(40)
Current assets:
Contracts in progress		(14)			(14)
Current liabilities:
Income taxes payable		(1)			(1)
Stockholders' equity:
Retained earnings	[3]	$ (13)			$ (13)

[1] Intercompany transactions were not significant for the three and nine months ended September 30, 2018 and 2017, respectively.

[2] Costs incurred in excess of costs recognized (assets) and costs recognized in excess of costs incurred (liabilities) resulted from the exclusion of certain costs when measuring progress toward completion under the cost-to-cost method, prior to our adoption of ASC Topic 606. These remaining amounts will be recognized in Cost of operations as the underlying projects progress.

[3] Includes $20 million of cumulative catch-up adjustment to Retained earnings (Accumulated deficit) on January 1, 2018, upon adoption of ASC 606.