Trade Accounts Receivable (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Trade Accounts Receivable
Total trade accounts receivable	$ 180,061,000	$ 228,267,000
Allowance for doubtful accounts	(14,806,000)	(16,894,000)
Total trade accounts receivable, net	165,255,000	211,373,000
Progress billings offset against contracts in process	6,300,000	5,400,000
Trade accounts receivables
Trade Accounts Receivable
Total trade accounts receivable	167,626,000	188,463,000
Contracts in process, net
Trade Accounts Receivable
Total trade accounts receivable	$ 12,435,000	$ 39,804,000