Schedule III - Real Estate and Accumulated Depreciation (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) property	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	3,795
Encumbrances at December 31, 2020	$ 1,305,445
Land	2,743,527
Buildings, Fixtures and Improvements	10,059,594
Costs Capitalized Subsequent to Acquisition	(71,956)
Gross Amount Carried at December 31, 2020	12,731,165	$ 12,939,229	$ 13,592,440	$ 13,577,700
Accumulated Depreciation	$ (2,920,134)	$ (2,727,099)	$ (2,622,879)	$ (2,217,108)
Administration & Support Services
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	3
Encumbrances at December 31, 2020	$ 0
Land	6,537
Buildings, Fixtures and Improvements	35,797
Costs Capitalized Subsequent to Acquisition	(4,501)
Gross Amount Carried at December 31, 2020	37,833
Accumulated Depreciation	$ (7,967)
Agricultural
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	2
Encumbrances at December 31, 2020	$ 0
Land	1,727
Buildings, Fixtures and Improvements	13,422
Costs Capitalized Subsequent to Acquisition	0
Gross Amount Carried at December 31, 2020	15,149
Accumulated Depreciation	$ (4,280)
Education
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	3
Encumbrances at December 31, 2020	$ 0
Land	3,170
Buildings, Fixtures and Improvements	22,706
Costs Capitalized Subsequent to Acquisition	(3,435)
Gross Amount Carried at December 31, 2020	22,441
Accumulated Depreciation	$ (4,739)
Entertainment & Recreation
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	38
Encumbrances at December 31, 2020	$ 4,749
Land	100,708
Buildings, Fixtures and Improvements	356,032
Costs Capitalized Subsequent to Acquisition	2,048
Gross Amount Carried at December 31, 2020	458,788
Accumulated Depreciation	$ (63,432)
Finance
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	149
Encumbrances at December 31, 2020	$ 128,114
Land	88,122
Buildings, Fixtures and Improvements	360,180
Costs Capitalized Subsequent to Acquisition	(10,518)
Gross Amount Carried at December 31, 2020	437,784
Accumulated Depreciation	$ (112,279)
Government & Public Services
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	7
Encumbrances at December 31, 2020	$ 2,600
Land	4,587
Buildings, Fixtures and Improvements	38,090
Costs Capitalized Subsequent to Acquisition	(2,244)
Gross Amount Carried at December 31, 2020	40,433
Accumulated Depreciation	$ (12,387)
Healthcare
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	6
Encumbrances at December 31, 2020	$ 17,751
Land	15,368
Buildings, Fixtures and Improvements	107,840
Costs Capitalized Subsequent to Acquisition	3,072
Gross Amount Carried at December 31, 2020	126,280
Accumulated Depreciation	$ (46,970)
Information & Communication
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	4
Encumbrances at December 31, 2020	$ 10,367
Land	5,652
Buildings, Fixtures and Improvements	56,729
Costs Capitalized Subsequent to Acquisition	4,076
Gross Amount Carried at December 31, 2020	66,457
Accumulated Depreciation	$ (18,827)
Insurance
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	7
Encumbrances at December 31, 2020	$ 58,798
Land	29,184
Buildings, Fixtures and Improvements	236,424
Costs Capitalized Subsequent to Acquisition	3,772
Gross Amount Carried at December 31, 2020	269,380
Accumulated Depreciation	$ (64,530)
Logistics
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	44
Encumbrances at December 31, 2020	$ 26,100
Land	50,877
Buildings, Fixtures and Improvements	299,486
Costs Capitalized Subsequent to Acquisition	29,358
Gross Amount Carried at December 31, 2020	379,721
Accumulated Depreciation	$ (123,707)
Manufacturing
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	48
Encumbrances at December 31, 2020	$ 150,748
Land	92,446
Buildings, Fixtures and Improvements	946,216
Costs Capitalized Subsequent to Acquisition	(18,831)
Gross Amount Carried at December 31, 2020	1,019,831
Accumulated Depreciation	$ (255,355)
Mining & Natural Resources
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	4
Encumbrances at December 31, 2020	$ 0
Land	1,727
Buildings, Fixtures and Improvements	14,644
Costs Capitalized Subsequent to Acquisition	(2,858)
Gross Amount Carried at December 31, 2020	13,513
Accumulated Depreciation	$ (3,013)
Other Services
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	2
Encumbrances at December 31, 2020	$ 0
Land	2,937
Buildings, Fixtures and Improvements	30,794
Costs Capitalized Subsequent to Acquisition	(987)
Gross Amount Carried at December 31, 2020	32,744
Accumulated Depreciation	$ (6,645)
Professional Services
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	33
Encumbrances at December 31, 2020	$ 97,217
Land	47,520
Buildings, Fixtures and Improvements	358,603
Costs Capitalized Subsequent to Acquisition	8,713
Gross Amount Carried at December 31, 2020	414,836
Accumulated Depreciation	$ (122,043)
Rental
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	56
Encumbrances at December 31, 2020	$ 0
Land	25,044
Buildings, Fixtures and Improvements	77,794
Costs Capitalized Subsequent to Acquisition	(626)
Gross Amount Carried at December 31, 2020	102,212
Accumulated Depreciation	$ (19,145)
Restaurants - Casual Dining
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	545
Encumbrances at December 31, 2020	$ 30,860
Land	406,606
Buildings, Fixtures and Improvements	936,599
Costs Capitalized Subsequent to Acquisition	(18,142)
Gross Amount Carried at December 31, 2020	1,325,063
Accumulated Depreciation	$ (291,230)
Restaurants - Quick Service
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	891
Encumbrances at December 31, 2020	$ 0
Land	412,840
Buildings, Fixtures and Improvements	803,854
Costs Capitalized Subsequent to Acquisition	(37,032)
Gross Amount Carried at December 31, 2020	1,179,662
Accumulated Depreciation	$ (277,662)
Retail - Apparel & Jewelry
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	11
Encumbrances at December 31, 2020	$ 45,872
Land	20,420
Buildings, Fixtures and Improvements	161,347
Costs Capitalized Subsequent to Acquisition	0
Gross Amount Carried at December 31, 2020	181,767
Accumulated Depreciation	$ (51,647)
Retail - Department Stores
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	12
Encumbrances at December 31, 2020	$ 7,705
Land	28,136
Buildings, Fixtures and Improvements	77,084
Costs Capitalized Subsequent to Acquisition	304
Gross Amount Carried at December 31, 2020	105,524
Accumulated Depreciation	$ (22,311)
Retail - Discount
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	810
Encumbrances at December 31, 2020	$ 81,232
Land	201,144
Buildings, Fixtures and Improvements	711,594
Costs Capitalized Subsequent to Acquisition	49,993
Gross Amount Carried at December 31, 2020	962,731
Accumulated Depreciation	$ (240,707)
Retail - Electronics & Appliances
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	12
Encumbrances at December 31, 2020	$ 0
Land	26,192
Buildings, Fixtures and Improvements	93,769
Costs Capitalized Subsequent to Acquisition	5,029
Gross Amount Carried at December 31, 2020	124,990
Accumulated Depreciation	$ (20,429)
Retail - Gas & Convenience
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	175
Encumbrances at December 31, 2020	$ 0
Land	107,424
Buildings, Fixtures and Improvements	258,729
Costs Capitalized Subsequent to Acquisition	(852)
Gross Amount Carried at December 31, 2020	365,301
Accumulated Depreciation	$ (76,670)
Retail - Grocery & Supermarket
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	65
Encumbrances at December 31, 2020	$ 69,243
Land	109,371
Buildings, Fixtures and Improvements	437,514
Costs Capitalized Subsequent to Acquisition	551
Gross Amount Carried at December 31, 2020	547,436
Accumulated Depreciation	$ (128,939)
Retail - Hobby, Books & Music
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	11
Encumbrances at December 31, 2020	$ 0
Land	24,569
Buildings, Fixtures and Improvements	113,995
Costs Capitalized Subsequent to Acquisition	505
Gross Amount Carried at December 31, 2020	139,069
Accumulated Depreciation	$ (14,534)
Retail - Home & Garden
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	105
Encumbrances at December 31, 2020	$ 76,815
Land	187,171
Buildings, Fixtures and Improvements	508,529
Costs Capitalized Subsequent to Acquisition	3,545
Gross Amount Carried at December 31, 2020	699,245
Accumulated Depreciation	$ (132,185)
Retail - Home Furnishings
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	51
Encumbrances at December 31, 2020	$ 1,194
Land	78,530
Buildings, Fixtures and Improvements	225,249
Costs Capitalized Subsequent to Acquisition	(4,828)
Gross Amount Carried at December 31, 2020	298,951
Accumulated Depreciation	$ (25,843)
Retail - Internet
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	1
Encumbrances at December 31, 2020	$ 40,800
Land	1,995
Buildings, Fixtures and Improvements	54,332
Costs Capitalized Subsequent to Acquisition	0
Gross Amount Carried at December 31, 2020	56,327
Accumulated Depreciation	$ (15,984)
Retail - Medical Services
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	58
Encumbrances at December 31, 2020	$ 6,615
Land	16,817
Buildings, Fixtures and Improvements	103,492
Costs Capitalized Subsequent to Acquisition	(2,846)
Gross Amount Carried at December 31, 2020	117,463
Accumulated Depreciation	$ (30,681)
Retail - Motor Vehicle
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	228
Encumbrances at December 31, 2020	$ 21,630
Land	107,294
Buildings, Fixtures and Improvements	483,183
Costs Capitalized Subsequent to Acquisition	3,360
Gross Amount Carried at December 31, 2020	593,837
Accumulated Depreciation	$ (155,326)
Retail - Office Supply
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	2
Encumbrances at December 31, 2020	$ 0
Land	2,698
Buildings, Fixtures and Improvements	5,806
Costs Capitalized Subsequent to Acquisition	0
Gross Amount Carried at December 31, 2020	8,504
Accumulated Depreciation	$ (1,664)
Retail - Pet Supply
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	16
Encumbrances at December 31, 2020	$ 51,250
Land	30,025
Buildings, Fixtures and Improvements	166,076
Costs Capitalized Subsequent to Acquisition	751
Gross Amount Carried at December 31, 2020	196,852
Accumulated Depreciation	$ (42,694)
Retail - Pharmacy
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	196
Encumbrances at December 31, 2020	$ 196,141
Land	202,670
Buildings, Fixtures and Improvements	671,059
Costs Capitalized Subsequent to Acquisition	(22,469)
Gross Amount Carried at December 31, 2020	851,260
Accumulated Depreciation	$ (223,869)
Retail - Specialty (Other)
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	8
Encumbrances at December 31, 2020	$ 1,454
Land	8,390
Buildings, Fixtures and Improvements	38,788
Costs Capitalized Subsequent to Acquisition	797
Gross Amount Carried at December 31, 2020	47,975
Accumulated Depreciation	$ (13,383)
Retail - Sporting Goods
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	27
Encumbrances at December 31, 2020	$ 12,255
Land	62,693
Buildings, Fixtures and Improvements	241,454
Costs Capitalized Subsequent to Acquisition	55
Gross Amount Carried at December 31, 2020	304,202
Accumulated Depreciation	$ (47,748)
Retail - Warehouse Clubs
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	15
Encumbrances at December 31, 2020	$ 74,897
Land	64,195
Buildings, Fixtures and Improvements	232,949
Costs Capitalized Subsequent to Acquisition	407
Gross Amount Carried at December 31, 2020	297,551
Accumulated Depreciation	$ (65,057)
Other
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Number of Properties | property	150
Encumbrances at December 31, 2020	$ 91,038
Land	168,741
Buildings, Fixtures and Improvements	779,435
Costs Capitalized Subsequent to Acquisition	(58,123)
Gross Amount Carried at December 31, 2020	890,053
Accumulated Depreciation	$ (176,252)