Accounts Receivable and Inventories (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Accounts receivable
Trade accounts receivable	$ 650,340		$ 636,304
Less: Allowance for doubtful accounts	(18,695)		(17,829)
Trade accounts receivable, net	631,645		618,475
Other receivables	34,955		44,431
Provision for doubtful accounts related to trade accounts receivable	2,927	2,166
Inventories
Finished goods	84,087		78,445
Work-in-process	44,832		34,041
Raw materials and purchased parts	93,364		92,995
Stores and supplies	39,676		36,453
Total inventories	$ 261,959		$ 241,934