Accounts Receivable (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Accounts Receivable [Abstract]
Trade accounts receivable	$ 152,120	$ 154,296
Revenue in excess of progress billings	10,680	20,525
Less: allowance for doubtful accounts	(10,427)	(11,274)
Total Accounts Receivable	$ 152,373	$ 163,547