Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) segment properties	Dec. 31, 2017 USD ($) properties	Dec. 31, 2016 USD ($)	Apr. 06, 2017 USD ($)
number of properties sold			9
Deferred financing costs, net	$ 33,941,000	$ 32,852,000
Number of Reportable Operating Segments | segment	4
Accounting for Acquisitions [Abstract]
Transaction costs	$ 3,698,000	523,000	$ 7,869,000
Goodwill	693,000	693,000
Intangible Assets, Net (Including Goodwill)	42,491,000	28,869,000
Amortization of above/below market leases and tenant allowances, net	581,000	107,000	(183,000)
Below Market Lease, Net	(8,100,000)	(8,792,000)		$ (7,611,000)
Revenue Recognition [Abstract]
Straight Line Rent	10,200,000	4,300,000	17,000,000
Tenant Reimbursements	15,400,000	15,600,000	15,600,000
Percentage rents	10,700,000	7,800,000	4,700,000
Participating interest income	0	700,000	800,000
prepayment fee	$ 74,700,000	800,000	3,600,000
Income Tax Disclosure [Abstract]
Percent of taxable income distributed to shareholders annually	90.00%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	35.00%
Current Federal Tax Expense (Benefit)	$ 0
Deferred TRS Income Tax Expense (Benefit)	$ (319,000)	$ (137,000)	$ (273,000)
Effective Income Tax Rate Reconciliation, Percent	0.80%	0.90%	0.20%
Other	$ 10,760,000	$ 12,118,000
Enacted Corporate tax rate, percent	21.00%
Deferred Tax Assets, Gross	$ 14,111,000	16,015,000
Deferred Tax Liabilities, Gross	3,351,000	3,897,000
Deferred Tax Liabilities	729,000
Current Income and Withholding Tax Expense	(1,700,000)	1,600,000	$ 1,700,000
Provision for income tax expense	0	0	0
Concentration Risks, Types, No Concentration Percentage [Abstract]
Rental revenue	556,363,000	484,203,000	415,184,000
Share-based Compensation [Abstract]
Share based compensation	$ 15,111,000	14,142,000	11,164,000
Share based compensation, future vesting period minimum (in years)	4 years
Share-based compensation expense included in severance expense	$ 3,218,000	0	0
Severance expense	$ 5,938,000	$ 0	$ 0
Impaired notes receivable	0	0	0
Straight Line Rent Adjustments	$ 25,000,000
American Multi-Cinema, Inc. [Member]
Concentration Risks, Types, No Concentration Percentage [Abstract]
Percent of megaplex theatre rental leased by AMC	34.00%
Rental revenue	$ 115,800,000	$ 114,400,000	$ 90,000,000
Percentage of lease revenue in total revenue	16.50%	19.90%	18.20%
Carmike Cinemas, Inc [Member]
Concentration Risks, Types, No Concentration Percentage [Abstract]
Rental revenue			$ 21,700,000
Percentage of lease revenue in total revenue			4.40%
Leases, Acquired-in-Place [Member]
Accounting for Acquisitions [Abstract]
Intangible assets, accumulated amortization	$ 7,700,000	$ 5,500,000
Weighted average useful life for in-place leases	10 years 10 months 15 days
Finite-Lived Intangible Assets, Future Amortization Expense [Abstract]
2019	$ 3,109,000
2020	2,834,000
2021	2,466,000
2022	1,826,000
2023	1,777,000
Thereafter	9,737,000
Total	21,749,000	21,512,000
Lease Agreements [Member]
Accounting for Acquisitions [Abstract]
Amortization	2,900,000	2,000,000	$ 1,400,000
Above Market Leases [Member]
Accounting for Acquisitions [Abstract]
Intangible assets, accumulated amortization	$ 1,000,000	800,000
Weighted average useful life for in-place leases	4 years 1 month
Finite-Lived Intangible Assets, Future Amortization Expense [Abstract]
2019	$ 101,000
2020	6,000
2021	6,000
2022	6,000
2023	6,000
Thereafter	29,000
Total	154,000	351,000
Trade Names [Member]
Accounting for Acquisitions [Abstract]
Intangible assets, accumulated amortization	53,000	23,000
Non-amortizing indefinite lived trade names	$ 5,400,000	5,400,000
Weighted average useful life for in-place leases	30 years 6 months 27 days
Finite-Lived Intangible Assets, Future Amortization Expense [Abstract]
2019	$ 125,000
2020	125,000
2021	125,000
2022	125,000
2023	125,000
Thereafter	3,132,000
Total	3,757,000
Indefinite and Finite-lived Intangible Assets, net	9,110,000	6,313,000
Below market leases [Member]
Accounting for Acquisitions [Abstract]
Intangible assets, accumulated amortization	$ 700,000	0
Weighted average useful life for in-place leases	31 years
Finite-Lived Intangible Assets, Future Amortization Expense [Abstract]
2019	$ 450,000
2020	438,000
2021	408,000
2022	373,000
2023	351,000
Thereafter	6,080,000
Total	8,100,000
Contract Value, intangible [Member]
Accounting for Acquisitions [Abstract]
Intangible assets, accumulated amortization	$ 200,000	0
Weighted average useful life for in-place leases	29 years 6 months
Finite-Lived Intangible Assets, Future Amortization Expense [Abstract]
2019	$ 365,000
2020	365,000
2021	365,000
2022	365,000
2023	365,000
Thereafter	8,960,000
Total	10,785,000	0
CANADA
Income Tax Disclosure [Abstract]
Other	10,000,000
Minimum [Member]
Operating Lease, Right-of-Use Asset	210,000,000
Operating Lease, Liability	$ 235,000,000
Share-based Compensation [Abstract]
Share based compensation, future vesting period minimum (in years)	3 years
Minimum [Member] | Building [Member]
Rental Properties [Abstract]
Estimated useful live of buildings (in years)	30 years
Minimum [Member] | Furniture and Fixtures [Member]
Rental Properties [Abstract]
Estimated useful live of buildings (in years)	3 years
Minimum [Member] | Building Improvements [Member]
Rental Properties [Abstract]
Estimated useful live of buildings (in years)	10 years
Maximum [Member]
Operating Lease, Right-of-Use Asset	$ 220,000,000
Operating Lease, Liability	$ 245,000,000
Share-based Compensation [Abstract]
Share based compensation, future vesting period minimum (in years)	4 years
Maximum [Member] | Building [Member]
Rental Properties [Abstract]
Estimated useful live of buildings (in years)	40 years
Maximum [Member] | Furniture and Fixtures [Member]
Rental Properties [Abstract]
Estimated useful live of buildings (in years)	25 years
Maximum [Member] | Building Improvements [Member]
Rental Properties [Abstract]
Estimated useful live of buildings (in years)	20 years
Stock Options [Member]
Share-based Compensation [Abstract]
Share based compensation, future vesting period minimum (in years)	4 years
Stock or Unit Option Plan Expense	$ 300,000	700,000	900,000
Restricted Stock [Member] | Employee [Member]
Share-based Compensation [Abstract]
Share based compensation expense related to employees and trustees	$ 13,500,000	12,200,000	9,200,000
Restricted Stock [Member] | Minimum [Member] | Employee [Member]
Share-based Compensation [Abstract]
Share based compensation, future vesting period minimum (in years)	3 years
Restricted Stock [Member] | Maximum [Member] | Employee [Member]
Share-based Compensation [Abstract]
Share based compensation, future vesting period minimum (in years)	4 years
Restricted Stock Units (RSUs) [Member] | Non-Employee Trustees [Member]
Share-based Compensation [Abstract]
Share based compensation expense related to employees and trustees	$ 1,300,000	1,300,000	1,100,000
Allowance for Doubtful Accounts [Member]
Allowance for Doubtful Accounts [Abstract]
Allowance for doubtful accounts	2,899,000	7,485,000	871,000
Employee Severance [Member] | Accelerated Vesting of Shares [Member] | Chief Investment Officer [Member] | Nonvested Shares [Member]
Share-based Compensation [Abstract]
Severance expense	$ 3,200,000
Theatre Project China Member | CHINA
Income Tax Disclosure [Abstract]
Number of Real Estate Properties | properties	4
Payments Related to Tax Withholding for Repatriation of Foreign Earnings	$ 62,000	$ 44,000
Education Property [Member]
number of properties sold		3
Education Reportable Operating Segment [Member]
Concentration Risks, Types, No Concentration Percentage [Abstract]
Rental revenue	102,642,000	$ 79,031,000	$ 77,775,000
Education Reportable Operating Segment [Member] | Education Property [Member]
number of properties sold | properties		2
Share-based Compensation [Abstract]
Mortgage Note Receivable from Property Sale		$ 12,300,000
Revolving Credit Facility [Member]
Deferred financing costs, net	$ 5,000,000	$ 6,500,000