Investigations, Claims, And Litigation (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) frigates	Dec. 31, 2016 USD ($)
Bolivarian Republic of Venezuela [Member]
Loss Contingencies
Number of foreign-built frigates | frigates	2
Arbitration Claim	$ 173.0
Monetary damages	$ 61.0
Ingalls Timecharging Investigation [Member]
Loss Contingencies
Contract receivable retainage initially withheld		$ 24.0
United States Navy | Ingalls Timecharging Investigation [Member]
Loss Contingencies
Contract receivable retainage initially withheld		18.2
Contract receivable retainage		4.7
United States Coast Guard | Ingalls Timecharging Investigation [Member]
Loss Contingencies
Contract receivable retainage initially withheld		5.8
Contract receivable retainage		$ 3.6