Summary of Significant Accounting Policies - Internal Use Software, RR & IT (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue Recognition
Increase to rental revenue	$ 500	$ 600	$ 800
Allowance for doubtful accounts (in dollars)	56	112
Asset Retirement and Environmental Remediation Obligations
Asset retirement and environmental remediation obligations	$ 1,700	$ 2,300
Income taxes
Minimum percentage of distribution of taxable income to qualify as REIT	90.00%
Percentage of distribution of taxable income as per company policy	100.00%
Provision for federal income taxes	$ 0
Liabilities for uncertain positions	$ 0

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The valuation allowance as of the balance sheet date to reduce the gross amount of receivables to estimated net realizable value, which would be presented in parentheses on the face of the balance sheet.

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Amount of non-cash amortization of intangible asset (liability) for above and below market leases.

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The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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Amount of current federal tax expense (benefit) pertaining to income (loss) from continuing operations.

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