Schedule III - Real Estate and Accumulated Depreciation and Amortization - Real Estate - Held for Sale (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Gross Amount at Which Carried at Close of Period, Land, Building, Improvements & Leasehold Interests	$ 8,448,702	$ 7,883,633	$ 7,314,132	$ 6,647,597
Accumulated Depreciation and Amortization	1,151,667	$ 1,016,271	$ 881,121	$ 742,467
Assets Held-for-sale
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company, Land	4,997
Initial Cost to Company, Building, Improvements & Leasehold Interests	6,510
Costs Capitalized Subsequent to Acquisition, Improvements	0
Costs Capitalized Subsequent to Acquisition, Carrying Costs	0
Gross Amount at Which Carried at Close of Period, Land	4,739
Gross Amount at Which Carried at Close of Period, Building, Improvements & Leasehold Interests	5,661
Gross Amount at Which Carried at Close of Period, Land, Building, Improvements & Leasehold Interests	10,400
Accumulated Depreciation and Amortization	3,390
Bloomsburg, PA 1 [Member] | Assets Held-for-sale | Fuel-On [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company, Land	541
Initial Cost to Company, Building, Improvements & Leasehold Interests	146
Costs Capitalized Subsequent to Acquisition, Improvements	0
Costs Capitalized Subsequent to Acquisition, Carrying Costs	0
Gross Amount at Which Carried at Close of Period, Land	311
Gross Amount at Which Carried at Close of Period, Building, Improvements & Leasehold Interests	105
Gross Amount at Which Carried at Close of Period, Land, Building, Improvements & Leasehold Interests	416
Accumulated Depreciation and Amortization	$ 105
Life on Which Depreciation & Amortization in Latest Income Statement is Computed	40 years
Danville, PA 1 [Member] | Assets Held-for-sale | Fuel-On [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost to Company, Land	180
Initial Cost to Company, Building, Improvements & Leasehold Interests	359
Costs Capitalized Subsequent to Acquisition, Improvements	0
Costs Capitalized Subsequent to Acquisition, Carrying Costs	0
Gross Amount at Which Carried at Close of Period, Land	180
Gross Amount at Which Carried at Close of Period, Building, Improvements & Leasehold Interests	232
Gross Amount at Which Carried at Close of Period, Land, Building, Improvements & Leasehold Interests	412
Accumulated Depreciation and Amortization	$ 125
Life on Which Depreciation & Amortization in Latest Income Statement is Computed	40 years
Houston, TX 1 [Member] | Assets Held-for-sale | Mister Car Wash [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost to Company, Land	2,260
Initial Cost to Company, Building, Improvements & Leasehold Interests	1,806
Costs Capitalized Subsequent to Acquisition, Improvements	0
Costs Capitalized Subsequent to Acquisition, Carrying Costs	0
Gross Amount at Which Carried at Close of Period, Land	2,260
Gross Amount at Which Carried at Close of Period, Building, Improvements & Leasehold Interests	1,806
Gross Amount at Which Carried at Close of Period, Land, Building, Improvements & Leasehold Interests	4,066
Accumulated Depreciation and Amortization	$ 918
Life on Which Depreciation & Amortization in Latest Income Statement is Computed	25 years
McSherrystown, PA 1 [Member] | Assets Held-for-sale | Uni-Mart [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost to Company, Land	135
Initial Cost to Company, Building, Improvements & Leasehold Interests	365
Costs Capitalized Subsequent to Acquisition, Improvements	0
Costs Capitalized Subsequent to Acquisition, Carrying Costs	0
Gross Amount at Which Carried at Close of Period, Land	135
Gross Amount at Which Carried at Close of Period, Building, Improvements & Leasehold Interests	365
Gross Amount at Which Carried at Close of Period, Land, Building, Improvements & Leasehold Interests	500
Accumulated Depreciation and Amortization	$ 127
Life on Which Depreciation & Amortization in Latest Income Statement is Computed	40 years
Sacramento, CA 1 [Member] | Assets Held-for-sale | Vacant Property [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost to Company, Land	1,144
Initial Cost to Company, Building, Improvements & Leasehold Interests	2,961
Costs Capitalized Subsequent to Acquisition, Improvements	0
Costs Capitalized Subsequent to Acquisition, Carrying Costs	0
Gross Amount at Which Carried at Close of Period, Land	1,144
Gross Amount at Which Carried at Close of Period, Building, Improvements & Leasehold Interests	2,462
Gross Amount at Which Carried at Close of Period, Land, Building, Improvements & Leasehold Interests	3,606
Accumulated Depreciation and Amortization	$ 1,703
Life on Which Depreciation & Amortization in Latest Income Statement is Computed	40 years
Bay City, MI 1 [Member] | Assets Held-for-sale | Vacant Property [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost to Company, Land	647
Initial Cost to Company, Building, Improvements & Leasehold Interests	634
Costs Capitalized Subsequent to Acquisition, Improvements	0
Costs Capitalized Subsequent to Acquisition, Carrying Costs	0
Gross Amount at Which Carried at Close of Period, Land	647
Gross Amount at Which Carried at Close of Period, Building, Improvements & Leasehold Interests	561
Gross Amount at Which Carried at Close of Period, Land, Building, Improvements & Leasehold Interests	1,208
Accumulated Depreciation and Amortization	$ 282
Life on Which Depreciation & Amortization in Latest Income Statement is Computed	40 years
Chicago, IL 1 [Member] | Assets Held-for-sale | Vacant Property [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost to Company, Land	90
Initial Cost to Company, Building, Improvements & Leasehold Interests	239
Costs Capitalized Subsequent to Acquisition, Improvements	0
Costs Capitalized Subsequent to Acquisition, Carrying Costs	0
Gross Amount at Which Carried at Close of Period, Land	62
Gross Amount at Which Carried at Close of Period, Building, Improvements & Leasehold Interests	130
Gross Amount at Which Carried at Close of Period, Land, Building, Improvements & Leasehold Interests	192
Accumulated Depreciation and Amortization	$ 130
Life on Which Depreciation & Amortization in Latest Income Statement is Computed	40 years