Trade Accounts Receivable, Net Of Allowances (Schedule Of Unbilled Trade Accounts Receivable) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 108,108	$ 99,219
Allowance for doubtful accounts		(31)
Allowance for sales credit memos	(1,256)	(895)
Total allowance	(1,256)	(926)
Total accounts receivable, net	106,852	98,293
Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	74,846	77,123
Unbilled Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 33,262	$ 22,096