Receivables (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Receivables
Trade accounts receivable	$ 759.3	$ 800.0
Less allowances for doubtful accounts	(5.4)	(7.0)
Net trade accounts receivable	753.9	793.0
Other receivables	131.5	164.1
Receivables, net	885.4	957.1
Net accounts receivable under long-term contracts, due primarily from agencies of the U.S government and their prime contractors	196.2	205.8
Recognized sales value of performance not billed and not yet billable to customers	$ 144.7	133.3
Average length of long-term contracts	2 years 6 months
Average remaining length of contracts	11 months
Customary fees and cost withholdings that will be paid upon milestone or contract completions	$ 195.1
Maximum available sale of the accounts receivables under factoring program	600.0
Amount of sale of receivables	$ 478.7	$ 197.6