Recent Acquisitions of Real Estate (Asset Acquisitions) (Details) $ in Thousands, € in Millions, £ in Millions																						12 Months Ended
	Dec. 12, 2019 USD ($) $ / £	Dec. 12, 2019 GBP (£) $ / £	Nov. 18, 2019 USD ($) $ / £	Nov. 18, 2019 GBP (£) $ / £	Nov. 14, 2019 USD ($)	Nov. 12, 2019 USD ($)	Nov. 08, 2019 USD ($) $ / £	Nov. 08, 2019 GBP (£) $ / £	Sep. 27, 2019 USD ($) $ / £	Sep. 27, 2019 GBP (£) $ / £	Sep. 26, 2019 USD ($) $ / €	Sep. 26, 2019 EUR (€)	Sep. 24, 2019 USD ($)	Sep. 13, 2019 USD ($)	May 03, 2019 USD ($) $ / €	May 03, 2019 EUR (€) $ / €	Dec. 31, 2018 USD ($)	Oct. 05, 2018 USD ($)	Sep. 21, 2018 USD ($)	Mar. 24, 2017 USD ($)	Jan. 06, 2017 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Oct. 11, 2017 USD ($)
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Right of Use Asset, net																	$ 0					$ 37,606	$ 0
Net Assets Acquired
Investments in acquired properties and lease intangibles																						620,974	206,782	$ 192,867
Lease term																									999 years
Operating lease liability																	0					$ 1,583	$ 0	$ 0
Rookwood
Net Assets Acquired
Building and Improvements																					$ 132,466
Land																					45,320
In-place lease intangibles																					27,477
Out-of-market lease intangibles, net																					(12,275)
Discount (premium) on assumed mortgage loan																					740
Total																					$ 193,728
Rookwood | In-Place Leases
Net Assets Acquired
Weighted average amortization period, in-place and above-market lease assets																					8 years 3 months 18 days
Rookwood | Out-of-Market Lease Assets
Net Assets Acquired
Weighted average amortization period, in-place and above-market lease assets																					15 years 8 months 12 days
Montrose Student Residences
Net Assets Acquired
Building and Improvements																				$ 33,705
Land																				5,691
In-place lease intangibles																				1,282
Out-of-market lease intangibles, net																				(56)
Discount (premium) on assumed mortgage loan																				0
Total																				40,622
Montrose Student Residences | Retail Site
Net Assets Acquired
In-place lease intangibles																				$ 600
Montrose Student Residences | Retail Site | Minimum
Net Assets Acquired
Lease term																				2 years
Montrose Student Residences | Retail Site | Maximum
Net Assets Acquired
Lease term																				19 years
Montrose Student Residences | In-Place Leases
Net Assets Acquired
Weighted average amortization period, in-place and above-market lease assets																				6 years 6 months
Montrose Student Residences | Out-of-Market Lease Assets
Net Assets Acquired
Weighted average amortization period, in-place and above-market lease assets																				0 years
Queen’s Court Student Residences
Net Assets Acquired
Building and Improvements																									$ 50,894
Land																									14,086
In-place lease intangibles																									1,819
Out-of-market lease intangibles, net																									(1,513)
Discount (premium) on assumed mortgage loan																									0
Total																									$ 65,286
ABC Westland
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Discount (premium) on assumed mortgage loan															$ 0
Total net purchase price															139,496
Net Assets Acquired
Investments in acquired properties and lease intangibles															$ 130,300	€ 116.4
Foreign currency exchange rate | $ / €															1.12	1.12
ABC Westland | Buildings and improvements
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment															$ 74,054
ABC Westland | Land
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment															59,664
ABC Westland | In-Place Leases
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
In-place Lease Intangibles															6,902
ABC Westland | Out-of-Market Lease Assets
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Out-of-Market Lease Intangibles, Net															(1,124)
ABC Westland | Solar Panels
Net Assets Acquired
Investments in acquired properties and lease intangibles															$ 15,800	€ 14.1
Foreign currency exchange rate | $ / €															1.12	1.12
Weighted average amortization period, in-place and above-market lease assets															25 years	25 years
The Promenade Shops at Briargate
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Discount (premium) on assumed mortgage loan														$ 0
Total net purchase price														93,594
Net Assets Acquired
Investments in acquired properties and lease intangibles														93,200
The Promenade Shops at Briargate | Buildings and improvements
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment														55,425
The Promenade Shops at Briargate | Land
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment														19,199
The Promenade Shops at Briargate | In-Place Leases
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
In-place Lease Intangibles														20,017
The Promenade Shops at Briargate | Out-of-Market Lease Assets
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Out-of-Market Lease Intangibles, Net														$ (1,047)
Gdansk PL II
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Discount (premium) on assumed mortgage loan													$ 0
Total net purchase price													30,343
Gdansk PL II | Buildings and improvements
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment													18,707
Gdansk PL II | Land
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment													6,174
Gdansk PL II | In-Place Leases
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
In-place Lease Intangibles													5,013
Gdansk PL II | Out-of-Market Lease Assets
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Out-of-Market Lease Intangibles, Net													$ 449
Lodz Urban Logistics
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Right of Use Asset, net											$ 2,777
Discount (premium) on assumed mortgage loan											0
Total net purchase price											25,625
Net Assets Acquired
Investments in acquired properties and lease intangibles											$ 25,200	€ 22.6
Foreign currency exchange rate | $ / €											1.11
Operating lease liability											$ 1,600
Lodz Urban Logistics | Buildings and improvements
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment											19,298
Lodz Urban Logistics | Land
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment											0
Lodz Urban Logistics | In-Place Leases
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
In-place Lease Intangibles											3,684
Lodz Urban Logistics | Out-of-Market Lease Assets
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Out-of-Market Lease Intangibles, Net											$ (134)
Glasgow West End
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Discount (premium) on assumed mortgage loan									$ 0
Total net purchase price									91,701
Net Assets Acquired
Investments in acquired properties and lease intangibles									$ 89,500	£ 72.0
Foreign currency exchange rate | $ / £									1.24	1.24
Glasgow West End | Buildings and improvements
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment									$ 66,255
Glasgow West End | Land
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment									22,276
Glasgow West End | In-Place Leases
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
In-place Lease Intangibles									3,170
Glasgow West End | Out-of-Market Lease Assets
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Out-of-Market Lease Intangibles, Net									$ 0
Charles Tyrwhitt DC
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Discount (premium) on assumed mortgage loan							$ 0
Total net purchase price							21,318
Net Assets Acquired
Investments in acquired properties and lease intangibles							$ 19,900	£ 15.5
Foreign currency exchange rate | $ / £							1.29	1.29
Charles Tyrwhitt DC | Buildings and improvements
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment							$ 11,207
Charles Tyrwhitt DC | Land
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment							7,013
Charles Tyrwhitt DC | In-Place Leases
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
In-place Lease Intangibles							3,587
Charles Tyrwhitt DC | Out-of-Market Lease Assets
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Out-of-Market Lease Intangibles, Net							$ (489)
The Alloy
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Discount (premium) on assumed mortgage loan						$ 0
Total net purchase price						99,441
Net Assets Acquired
Investments in acquired properties and lease intangibles					$ 98,000
The Alloy | Buildings and improvements
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment						81,956
The Alloy | Land
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment						14,194
The Alloy | In-Place Leases
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
In-place Lease Intangibles						3,291
The Alloy | Out-of-Market Lease Assets
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Out-of-Market Lease Intangibles, Net						$ 0
DSG Bristol
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Discount (premium) on assumed mortgage loan			$ 0
Total net purchase price			50,042
Net Assets Acquired
Investments in acquired properties and lease intangibles			$ 47,000	£ 36.6
Foreign currency exchange rate | $ / £			1.29	1.29
DSG Bristol | Buildings and improvements
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment			$ 22,503
DSG Bristol | Land
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment			17,713
DSG Bristol | In-Place Leases
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
In-place Lease Intangibles			8,319
DSG Bristol | Out-of-Market Lease Assets
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Out-of-Market Lease Intangibles, Net			$ 1,507
Royal Mail Edinburgh
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Discount (premium) on assumed mortgage loan	$ 0
Total net purchase price	35,441
Net Assets Acquired
Investments in acquired properties and lease intangibles	$ 33,400	£ 25.4
Foreign currency exchange rate | $ / £	1.31	1.31
Royal Mail Edinburgh | Buildings and improvements
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment	$ 23,735
Royal Mail Edinburgh | Land
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment	6,170
Royal Mail Edinburgh | In-Place Leases
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
In-place Lease Intangibles	5,536
Royal Mail Edinburgh | Out-of-Market Lease Assets
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Out-of-Market Lease Intangibles, Net	$ 0
Venue Museum District
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Discount (premium) on assumed mortgage loan																			$ 0
Total net purchase price																			73,187
Venue Museum District | Buildings and improvements
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment																			52,538
Venue Museum District | Land
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment																			17,409
Venue Museum District | In-Place Leases
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
In-place Lease Intangibles																			3,240
Venue Museum District | Out-of-Market Lease Assets
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Out-of-Market Lease Intangibles, Net																			$ 0
Fresh Park Venlo
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Discount (premium) on assumed mortgage loan																		$ 0
Total net purchase price																		138,274
Fresh Park Venlo | Buildings and improvements
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment																		128,977
Fresh Park Venlo | Land
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment																		0
Fresh Park Venlo | In-Place Leases
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
In-place Lease Intangibles																		11,880
Fresh Park Venlo | Out-of-Market Lease Assets
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Out-of-Market Lease Intangibles, Net																		$ (2,583)
Maintal Logistics
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Discount (premium) on assumed mortgage loan																	0
Total net purchase price																	46,802
Maintal Logistics | Buildings and improvements
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment																	30,175
Maintal Logistics | Land
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Property, plant and equipment																	15,031
Maintal Logistics | In-Place Leases
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
In-place Lease Intangibles																	2,287
Maintal Logistics | Out-of-Market Lease Assets
Asset Acquisition, Assets Acquired and Liabilities Assumed [Abstract]
Out-of-Market Lease Intangibles, Net																	$ (691)