Accounts Receivable and Inventories (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Accounts receivable
Trade accounts receivable	$ 640,941		$ 617,517
Less: Allowance for doubtful accounts	(18,785)		(17,253)
Trade accounts receivable, net	622,156		600,264
Other receivables	39,651		39,836
Provision for doubtful accounts related to trade accounts receivable	2,217	2,927
Inventories
Finished goods	70,419		69,904
Work-in-process	36,519		28,944
Raw materials and purchased parts	98,900		99,058
Stores and supplies	38,679		38,606
Inventories	$ 244,517		$ 236,512