Investigations, Claims, and Litigation (Details) (USD $) In Millions, unless otherwise specified	20 Months Ended
	Sep. 30, 2012 False Claims Act [Member] Minimum	Sep. 30, 2013 Ingalls Timecharging Investigation [Member]
Loss Contingencies
Monetary damages	$ 835
Contract receivable retainage initially withheld		24
Contract receivable retainage previously withheld		18.2
Contract receivable retainage		13.1
Customer estimate of misallocated costs and overstated progress		5.3
Estimate of misallocated costs and overstated progress		$ 4