Description of Business and Basis of Presentation (Recently Issued Accounting Standards) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	$ 118,706	$ 113,159	$ 352,536	$ 352,073
Net cash provided by operating activities			(178,037)	(161,229)
Net increase (decrease) in cash used in investing activities			(182,402)	(7,395)
Cumulative effect of change in accounting principle					$ 22,329
Distributions in Excess of Net Income
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle					22,329
Accounting Standards Update 2016-15 | New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by operating activities				33,600
Net increase (decrease) in cash used in investing activities				33,600
Accounting Standards Update 2016-18 | New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by operating activities				92
Net increase (decrease) in cash used in investing activities				(15,100)
Accounting Standards Update 2017-05 | Distributions in Excess of Net Income
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle					$ 22,300
Rental Property
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	115,443	109,569	342,489	336,093
Fee and Other Revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	$ 3,300	$ 3,600	$ 10,000	$ 16,000