Product Warranties (Details) (USD $)	3 Months Ended			6 Months Ended		9 Months Ended		3 Months Ended		6 Months Ended				12 Months Ended	3 Months Ended
	Sep. 30, 2012	Jun. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Jun. 30, 2011	Sep. 30, 2012 installment	Sep. 30, 2011	Jun. 30, 2012 Power supply devices	Jun. 30, 2011 Power supply devices	Jun. 30, 2011 Power supply devices	Sep. 30, 2012 Power supply devices	Dec. 31, 2011 Power supply devices	Sep. 30, 2011 Power supply devices	Dec. 31, 2011 Cost of sales	Dec. 31, 2011 Accrued expenses Power supply devices	Sep. 30, 2011 Accrued expenses Power supply devices	Sep. 30, 2011 Prepaid expenses and other assets	Jun. 30, 2011 Prepaid expenses and other assets
Product Liability Contingency [Line Items]
Reimbursements from suppliers										$ 1,000,000				$ 1,200,000
Warranty accrual	5,084,000	4,779,000	3,677,000	5,084,000	2,156,000	5,084,000	3,677,000					5,500,000	2,800,000
Previously recoognized warranty liability									1,300,000
Estimated product warranty liability											2,700,000					1,500,000
Product warranty expense															2,700,000
Product warranty payments								2,000,000
Reimbursement receivable		1,200,000			1,300,000												500,000	1,300,000
Reimbursement receivable, in the form of cash and/or note receivable					500,000
Cash received pursuant to settlement				700,000
Remaining reimbursement receivable after payment	500,000			500,000		500,000
Number of quarterly installments receivable						3
Period of product rebates/price concessions under settlement agreement		39 months
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance, beginning of period	4,779,000		2,156,000		982,000	6,871,000	982,000					5,500,000	2,800,000
Charges to operations	1,274,000		2,190,000			1,691,000	4,457,000
Deductions for costs incurred	(969,000)		(669,000)			(3,478,000)	(1,762,000)
Balance, end of period	$ 5,084,000	$ 4,779,000	$ 3,677,000	$ 5,084,000	$ 2,156,000	$ 5,084,000	$ 3,677,000					$ 5,500,000	$ 2,800,000