Equipment Acquisitions, Dispositions and Depreciation and Impairment Policies (Deferred Gain Activity) (Details) (USD $)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Equipment Acquisitions, Dispositions And Depreciation And Impairment Policies [Abstract]
Repayments of Lines of Credit	$ (9,400,000)
Deferred Gain on Sale of Property, Beginning of Period	124,763,000	111,514,000
Deferred Gains on Asset Sales	53,832,000	14,609,000
Amortization Of Deferred Gains Included in Operating Expenses As A Reduction To Rental Expense	(12,196,000)	(7,707,000)
Amortization Of Deferred Gains Included In Gains On Asset Dispositions And Impairments, Net	(3,484,000)	(2,146,000)
Deferred Gain on Sale of Property, End of Period	$ 162,915,000	$ 116,270,000