SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Income Taxes, Earnings per Share and Unit and Derivatives (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes
Net tax basis in the entity's assets	$ 3,909.1	$ 3,645.7
Percentage of distributions characterized as ordinary income dividends	78.413%
Percentage of distributions characterized as capital gain dividends	5.207%
Percentage of distributions characterized as return of capital dividends	16.38%
Federal excise tax rate (as a percent)	4.00%
Percentage of ordinary income considered for the calculation of annual amount which is subject to federal excise tax	85.00%
Percentage of net capital gain considered for the calculation of annual amount which is subject to Federal excise tax	95.00%
Percentage of prior year taxable income considered for the calculation of annual amount which is subject to federal excise tax	100.00%
Sales and Excise Tax Payable	$ 0.0
Net deferred tax asset recorded by REIT subsidiary TRS	$ 0.7	$ 1.4
Earnings per Share and Unit
Potential dilutive securities included in the calculation of diluted earnings per share (in shares)	702,000	842,000	923,000
Foreign currency
Derivatives outstanding	$ 0.0
Impairment	0.0	$ 0.0
Interest rate swap \| Designated \| Cash flow
Foreign currency
Notional principal amounts	$ 150.0

Represents the percentage of distributions characterized as capital gain dividends.

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Tax basis of real estate assets.

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Amount, before allocation of valuation allowances, of deferred tax asset attributable to deductible differences from reserves and accruals, compensation and benefit costs, and other provisions, reserves, and allowances.

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Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

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Nominal or face amount used to calculate payments on the derivative liability.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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Carrying value as of the balance sheet date of liabilities incurred through that date and payable for statutory sales and use taxes, including value added tax.

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