Investments in Real Estate - Summary of Wholly Owned Industrial Properties Acquired (Details) $ in Thousands																										12 Months Ended
	Dec. 19, 2019 USD ($) ft² building	Dec. 13, 2019 USD ($) ft² building	Nov. 15, 2019 USD ($) ft² a building	Aug. 30, 2019 USD ($) ft² building	Aug. 29, 2019 USD ($) ft² building	Aug. 21, 2019 USD ($) ft² building	Aug. 19, 2019 USD ($) ft² building	Aug. 07, 2019 USD ($) ft² a building	May 28, 2019 USD ($) ft² building	Mar. 29, 2019 USD ($) a ft² building	Mar. 08, 2019 USD ($) a ft² building	Feb. 12, 2019 USD ($) ft² building	Dec. 20, 2018 USD ($) ft² building	Nov. 14, 2018 USD ($) a ft² building	Nov. 07, 2018 USD ($) ft² building	Oct. 31, 2018 USD ($) ft² building	Oct. 24, 2018 USD ($) a ft² building	Oct. 17, 2018 USD ($) ft² building	Sep. 17, 2018 USD ($) a ft² building	Sep. 07, 2018 USD ($) ft² building	Aug. 02, 2018 USD ($) a ft² building	May 07, 2018 USD ($) ft² a building	Apr. 27, 2018 USD ($) ft² building	Mar. 06, 2018 USD ($) ft² building	Jan. 31, 2018 USD ($) ft² building	Dec. 31, 2019 USD ($) ft² a building property land_parcel	Dec. 31, 2018 USD ($) ft² building
Real Estate Properties [Line Items]
Number of properties | property																										220
Area of real estate property | a																										77.6
Improved land parcels [Member]
Real Estate Properties [Line Items]
Number of properties | land_parcel																										19
Area of real estate property | ft²																										13,300,000
Asset acquisitions 2019 [Member]
Real Estate Properties [Line Items]
Asset acquisitions, assets acquired and liabilities assumed, net																										$ 289,600
Asset acquisition																										$ 6,000
Asset acquisitions 2018 [Member]
Real Estate Properties [Line Items]
Purchase price																											$ 112,900
Asset acquisitions, assets acquired and liabilities assumed, net																											227,100
Asset acquisition																											$ 2,900
Wholly Owned Properties [Member] | Asset acquisitions 2019 [Member]
Real Estate Properties [Line Items]
Number of properties | building																										17
Area of real estate property | ft²																										699,104
Purchase price																										$ 273,610
Wholly Owned Properties [Member] | Asset acquisitions 2019 [Member] | 49th Street [Member]
Real Estate Properties [Line Items]
Number of properties | building												1
Area of real estate property | ft²												19,000
Purchase price												$ 24,017
Wholly Owned Properties [Member] | Asset acquisitions 2019 [Member] | 81 First N Hackensack [Member]
Real Estate Properties [Line Items]
Number of properties | building											0
Area of real estate property | ft²											0
Purchase price											$ 25,000
Wholly Owned Properties [Member] | Asset acquisitions 2019 [Member] | 81 First N Hackensack [Member] | Improved land parcels [Member]
Real Estate Properties [Line Items]
Area of real estate property | a											16.8
Wholly Owned Properties [Member] | Asset acquisitions 2019 [Member] | 48th 3rd and 286 [Member]
Real Estate Properties [Line Items]
Number of properties | building										1
Area of real estate property | ft²										28,124
Purchase price										$ 14,085
Wholly Owned Properties [Member] | Asset acquisitions 2019 [Member] | 48th 3rd and 286 [Member] | Improved land parcels [Member]
Real Estate Properties [Line Items]
Area of real estate property | a										2.9
Wholly Owned Properties [Member] | Asset acquisitions 2019 [Member] | Minnesota and Tennessee [Member]
Real Estate Properties [Line Items]
Number of properties | building									2
Area of real estate property | ft²									119,089
Purchase price									$ 47,775
Wholly Owned Properties [Member] | Asset acquisitions 2019 [Member] | 51 Kero [Member]
Real Estate Properties [Line Items]
Number of properties | building								0
Area of real estate property | ft²								0
Purchase price								$ 4,025
Wholly Owned Properties [Member] | Asset acquisitions 2019 [Member] | 51 Kero [Member] | Improved land parcels [Member]
Real Estate Properties [Line Items]
Area of real estate property | a								2.0
Wholly Owned Properties [Member] | Asset acquisitions 2019 [Member] | Anderson [Member]
Real Estate Properties [Line Items]
Number of properties | building							5
Area of real estate property | ft²							53,016
Purchase price							$ 18,100
Wholly Owned Properties [Member] | Asset acquisitions 2019 [Member] | Auburn 400 [Member]
Real Estate Properties [Line Items]
Number of properties | building						1
Area of real estate property | ft²						70,345
Purchase price						$ 9,450
Wholly Owned Properties [Member] | Asset acquisitions 2019 [Member] | Morgan [Member]
Real Estate Properties [Line Items]
Number of properties | building					2
Area of real estate property | ft²					195,598
Purchase price					$ 80,500
Wholly Owned Properties [Member] | Asset acquisitions 2019 [Member] | 20th Street [Member]
Real Estate Properties [Line Items]
Number of properties | building				1
Area of real estate property | ft²				92,884
Purchase price				$ 23,752
Wholly Owned Properties [Member] | Asset acquisitions 2019 [Member] | Slauson [Member]
Real Estate Properties [Line Items]
Number of properties | building				2
Area of real estate property | ft²				29,927
Purchase price				$ 5,331
Wholly Owned Properties [Member] | Asset acquisitions 2019 [Member] | East Marginal [Member]
Real Estate Properties [Line Items]
Number of properties | building			0
Area of real estate property | ft²			0
Purchase price			$ 2,850
Wholly Owned Properties [Member] | Asset acquisitions 2019 [Member] | East Marginal [Member] | Improved land parcels [Member]
Real Estate Properties [Line Items]
Area of real estate property | a			0.9
Wholly Owned Properties [Member] | Asset acquisitions 2019 [Member] | Whelan [Member]
Real Estate Properties [Line Items]
Number of properties | building		1
Area of real estate property | ft²		50,305
Purchase price		$ 12,000
Wholly Owned Properties [Member] | Asset acquisitions 2019 [Member] | 917 Valley [Member]
Real Estate Properties [Line Items]
Number of properties | building	1
Area of real estate property | ft²	40,816
Purchase price	$ 6,725
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member]
Real Estate Properties [Line Items]
Number of properties | building																											17
Area of real estate property | ft²																											1,038,889
Purchase price																											$ 219,490
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | Vermont [Member]
Real Estate Properties [Line Items]
Number of properties | building																									1
Area of real estate property | ft²																									99,629
Purchase price																									$ 17,500
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | Woodside [Member]
Real Estate Properties [Line Items]
Number of properties | building																								1
Area of real estate property | ft²																								83,294
Purchase price																								$ 25,170
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | 1st Avenue South [Member]
Real Estate Properties [Line Items]
Number of properties | building																								1
Area of real estate property | ft²																								234,720
Purchase price																								$ 42,000
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | Wicks Blvd [Member]
Real Estate Properties [Line Items]
Number of properties | building																							1
Area of real estate property | ft²																							11,300
Purchase price																							$ 2,600
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | 85 Doremus [Member]
Real Estate Properties [Line Items]
Number of properties | building																						0
Area of real estate property | ft²																						0
Purchase price																						$ 6,300
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | 85 Doremus [Member] | Improved land parcels [Member]
Real Estate Properties [Line Items]
Area of real estate property | a																						3.5
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | East Valley [Member]
Real Estate Properties [Line Items]
Number of properties | building																						1
Area of real estate property | ft²																						39,005
Purchase price																						$ 5,950
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | Merced [Member]
Real Estate Properties [Line Items]
Number of properties | building																					4
Area of real estate property | ft²																					225,344
Purchase price																					$ 36,000
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | Merced [Member] | Improved land parcels [Member]
Real Estate Properties [Line Items]
Area of real estate property | a																					1.2
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | San Clemente [Member]
Real Estate Properties [Line Items]
Number of properties | building																				1
Area of real estate property | ft²																				54,000
Purchase price																				$ 9,000
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | Whitney [Member]
Real Estate Properties [Line Items]
Number of properties | building																			3
Area of real estate property | ft²																			128,073
Purchase price																			$ 22,790
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | Whitney [Member] | Improved land parcels [Member]
Real Estate Properties [Line Items]
Area of real estate property | a																			0.2
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | Commerce [Member]
Real Estate Properties [Line Items]
Number of properties | building																		1
Area of real estate property | ft²																		24,000
Purchase price																		$ 3,480
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | Kent 192 [Member]
Real Estate Properties [Line Items]
Number of properties | building																	0
Area of real estate property | ft²																	0
Purchase price																	$ 12,434
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | Kent 192 [Member] | Improved land parcels [Member]
Real Estate Properties [Line Items]
Area of real estate property | a																	12.7
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | 6th Ave [Member]
Real Estate Properties [Line Items]
Number of properties | building																1
Area of real estate property | ft²																50,270
Purchase price																$ 12,558
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | Walnut II [Member]
Real Estate Properties [Line Items]
Number of properties | building															1
Area of real estate property | ft²															60,040
Purchase price															$ 11,108
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | Shoemaker [Member]
Real Estate Properties [Line Items]
Number of properties | building														0
Area of real estate property | ft²														0
Purchase price														$ 6,400
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | Shoemaker [Member] | Improved land parcels [Member]
Real Estate Properties [Line Items]
Area of real estate property | a														2.3
Wholly Owned Properties [Member] | Asset acquisitions 2018 [Member] | Hotchkiss II [Member]
Real Estate Properties [Line Items]
Number of properties | building													1
Area of real estate property | ft²													29,214
Purchase price													$ 6,200