Activity in Allowance for Doubtful Accounts (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended				9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Accounts Receivable Allowance for Doubtful Accounts Finance Leases	Dec. 31, 2010 Accounts Receivable Allowance for Doubtful Accounts Finance Leases	Sep. 30, 2012 Accounts Receivable Allowance for Doubtful Accounts Operating Leases	Dec. 31, 2010 Accounts Receivable Allowance for Doubtful Accounts Operating Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance			$ 11	$ 11	$ 10	$ 10	$ 1	$ 1
(Reversal of provision) provision	(154)	(35)	107	8	(10)		117
Ending Balance	$ 118		$ 118			$ 10	$ 118	$ 1