Guarantees (Tables)

12 Months Ended

Dec. 31, 2011

Guarantees [Abstract]

Changes in the carrying amount of service and product warranties

Changes in the carrying amount of service and product warranties for the year ended December 31, are as follows:

	2009			2010			2011
Balance as of January 1,	$	3,341		$	3,383		$	3,363
Provision for warranties	3,638			3,510			4,344
Claims made	(3,596		)	(3,530		)	(4,089		)
Balance as of December 31,	$	3,383		$	3,363		$	3,618