Warranty Reserves (Tables)

9 Months Ended

Sep. 30, 2012

Warranty Reserves [Abstract]

Changes in accrued warranty expense

	For the three months ended						For the nine months ended
	September 30,						September 30,
	2011			2012			2011			2012
	(Unaudited)			(Unaudited)			(Unaudited)			(Unaudited)
Beginning balance	$	172,583		$	140,307		$	155,918		$	135,708
Additions		62,241			21,939			196,354			71,897
Usage		(62,056	)		(4,331	)		(179,504	)		(49,690	)
Ending balance	$	172,768		$	157,915		$	172,768		$	157,915