Summary of Significant Accounting Policies - Narrative (Details) - USD ($)		3 Months Ended					6 Months Ended	9 Months Ended
	Jun. 02, 2015	Sep. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Mar. 31, 2015	Jun. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Jan. 31, 2016	Dec. 31, 2014
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Income tax expense (benefit)		$ 448,000			$ 703,000			$ 1,428,000	$ 3,646,000
Cash and cash equivalents		50,273,000		$ 69,938,000	32,080,000			50,273,000	32,080,000		$ 64,684,000
Cash out-flow from financing activities								120,942,000	(116,899,000)
Rental income		50,756,000			47,836,000			154,003,000	142,502,000
Accrued rent		14,040,000		15,491,000				14,040,000
Listing Amount, percent	15.00%
Cumulative, non-compounded, pre-tax annual return, percent	6.00%
Listing amount distribution measurement period (days)	30 days
Derivative liability		16,093,000		6,028,000				16,093,000
Deferred financing costs		$ 5,719,000		7,446,000				$ 5,719,000
Accounting Standards Update 2015-03 | Deferred financing costs, net
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Deferred financing costs				(7,400,000)
Accounting Standards Update 2015-03 | Mortgage notes payable
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Deferred financing costs				7,400,000
OPP
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Requisite service period (years)	5 years							5 years
Listing Note
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Derivative liability										$ 0
Adjustment | Not Designated as Hedging Instrument
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Gains recognized in other comprehensive income (loss)					$ 1,100,000	$ 500,000			$ 1,100,000
Reclassification from Cash and Cash Equivalents to Restricted Cash | Adjustment
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Cash and cash equivalents				1,700,000
Cash out-flow from financing activities			$ 1,700,000
Straight-Line Rent Effect, Termination Payments Under Lease Cancellation Clauses | Adjustment
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Rental income							$ 300,000
Accrued rent							300,000
Change in Tax Valuation | Adjustment
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Income tax expense (benefit)				$ 500,000			900,000
Deferred Tax Asset | Change in Tax Valuation | Adjustment
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Income tax expense (benefit)							300,000
Foreign Tax Authority | Change in Tax Valuation | Adjustment
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Income tax expense (benefit)							$ 1,200,000