Allowance for Credit Losses - Summary of Allowance for Credit Losses (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Dec. 31, 2010
Allowance for credit losses and recorded investment in financing receivables
Financing Receivable, Allowance for Credit Losses	$ 2,545	$ 1,747	$ 2,257	$ 848
Financing Receivable, Allowance for Credit Losses, Provisions	247	1,661
Financing Receivable, Allowance for Credit Losses, Recoveries	41	5,548
Financing Receivable, Allowance for Credit Losses, Charge-offs	0	(6,310)
Allowance resulting from individual impairment evaluation	2,545	1,747
Allowance resulting from collective impairment evaluation	0	0
Recorded investment in financing receivables
Balance individually evaluated for impairment	109,582	133,745
Balance collectively evaluated for impairment	0	0
Finance Leases Financing Receivable [Member]
Allowance for credit losses and recorded investment in financing receivables
Financing Receivable, Allowance for Credit Losses	498	127	210	378
Financing Receivable, Allowance for Credit Losses, Provisions	247	9
Financing Receivable, Allowance for Credit Losses, Recoveries	41	94
Financing Receivable, Allowance for Credit Losses, Charge-offs	0	(354)
Allowance resulting from individual impairment evaluation	498	127
Allowance resulting from collective impairment evaluation	0	0
Recorded investment in financing receivables
Balance individually evaluated for impairment	95,753	117,205
Balance collectively evaluated for impairment	0	0
Notes Receivable [Member]
Allowance for credit losses and recorded investment in financing receivables
Financing Receivable, Allowance for Credit Losses	2,047	1,620	2,047	470
Financing Receivable, Allowance for Credit Losses, Provisions	0	1,652
Financing Receivable, Allowance for Credit Losses, Recoveries	0	5,454
Financing Receivable, Allowance for Credit Losses, Charge-offs	0	(5,956)
Allowance resulting from individual impairment evaluation	2,047	1,620
Allowance resulting from collective impairment evaluation	0	0
Recorded investment in financing receivables
Balance individually evaluated for impairment	13,829	16,540
Balance collectively evaluated for impairment	$ 0	$ 0