Trade Accounts Receivable, Net Of Allowances (Activity Of Allowance For Sales Credit Memos) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Trade Accounts Receivable, Net Of Allowances [Abstract]
Balance at start of year	$ 1,027	$ 540	$ 1,125
Provision for credit memos	2,877	3,050	2,600
Credit memos issued	(3,009)	(2,563)	(3,185)
Balance at end of year	$ 895	$ 1,027	$ 540