Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Summary of Significant Accounting Policies (Textual) [Abstract]
Contract maintenance arrangements cancelable without penalty	after one year with 60 days prior written notice
Maximum amount of insurance risk of loss retained per occurrence	$ 3
Revenue recognition criteria description	typically when a customer is 120 days past due
Direct financing lease revenue recognition criteria description	generally over 120 days past due
Interest-bearing instruments maturities	Three months or less at the date of purchase