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Summary Of Significant Accounting Policies [Line Items]

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For an unclassified balance sheet, a valuation allowance for receivables due a company that are expected to be uncollectible.

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Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal, through the balance sheet date and due to be paid more than one year (or one operating cycle, if longer) after the balance sheet date.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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The net book value of the asset(s) sold in connection with the sale of the property to another party and lease back to the seller.

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Summary of Significant Accounting Policies (Additional Information 2) (Details) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($) segment subsidiary	Sep. 30, 2017	Dec. 31, 2017 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Aggregate allowance for doubtful accounts	$ 4.3		$ 11.5
Capital lease obligations	4.0		7.8
Lease financing obligations	0.3		0.9
Net book value of assets associated with leases	$ 3.3		$ 14.7
Number of operating segments \| segment	1
Number of reportable segments \| segment	1
Number of subsidiaries taxed as taxable REIT \| subsidiary	2
Effective tax rate	8.90%	46.40%
Statutory rate	21.00%		35.00%
Customer One \| Rental Revenue
Summary Of Significant Accounting Policies [Line Items]
Percentage of total revenue	12.60%
No Other Customers \| Rental Revenue \| Minimum
Summary Of Significant Accounting Policies [Line Items]
Percentage of total revenue	5.00%
Four Customers [Member] \| Accounts Receivable
Summary Of Significant Accounting Policies [Line Items]
Percentage of total accounts receivable	33.00%
Four Customers [Member] \| Accounts Receivable \| Minimum
Summary Of Significant Accounting Policies [Line Items]
Percentage of total accounts receivable	5.00%
One Customer \| Accounts Receivable \| Minimum
Summary Of Significant Accounting Policies [Line Items]
Percentage of total accounts receivable	10.00%