Real Estate Investments and Related Intangibles - Schedule of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assumed intangible liabilities:
Below market lease, weighted average useful life	18 years 8 months 14 days
In-place leases and other intangible assets [Member]
Assumed intangible liabilities:
Weighted-Average Useful Life	15 years 1 month 25 days
Above-market leases [Member]
Assumed intangible liabilities:
Weighted-Average Useful Life	16 years 3 months 17 days
2017 Acquisitions [Member]
Real estate investments, at cost:
Land	$ 110,634
Buildings, fixtures and improvements	523,445
Total tangible assets	634,079
Assumed intangible liabilities:
Total purchase price of assets acquired	748,784
2017 Acquisitions [Member] | In-place leases and other intangible assets [Member]
Acquired intangible assets:
Acquired intangible assets	$ 105,940
Assumed intangible liabilities:
Weighted-Average Useful Life	15 years 10 months 2 days
2017 Acquisitions [Member] | Above-market leases [Member]
Acquired intangible assets:
Acquired intangible assets	$ 10,445
Assumed intangible liabilities:
Weighted-Average Useful Life	18 years
2017 Acquisitions [Member] | Below-market leases [Member]
Assumed intangible liabilities:
Below-market leases	$ (1,680)
Below market lease, weighted average useful life	13 years 9 months 7 days
2016 Acquisitions [Member]
Real estate investments, at cost:
Land		$ 23,187
Buildings, fixtures and improvements		67,865
Total tangible assets		91,052
Assumed intangible liabilities:
Total purchase price of assets acquired		100,194
2016 Acquisitions [Member] | In-place leases and other intangible assets [Member]
Acquired intangible assets:
Acquired intangible assets		$ 9,613
Assumed intangible liabilities:
Weighted-Average Useful Life		13 years 9 months 18 days
2016 Acquisitions [Member] | Above-market leases [Member]
Acquired intangible assets:
Acquired intangible assets		$ 0
2016 Acquisitions [Member] | Below-market leases [Member]
Assumed intangible liabilities:
Below-market leases		$ (471)
Below market lease, weighted average useful life		10 years
2015, Acquisitions [Member]
Real estate investments, at cost:
Land			$ 5,051
Buildings, fixtures and improvements			28,643
Total tangible assets			33,694
Assumed intangible liabilities:
Total purchase price of assets acquired			36,319
2015, Acquisitions [Member] | In-place leases and other intangible assets [Member]
Acquired intangible assets:
Acquired intangible assets			$ 2,580
Assumed intangible liabilities:
Weighted-Average Useful Life			11 years
2015, Acquisitions [Member] | Above-market leases [Member]
Acquired intangible assets:
Acquired intangible assets			$ 153
Assumed intangible liabilities:
Weighted-Average Useful Life			14 years 1 month 10 days
2015, Acquisitions [Member] | Below-market leases [Member]
Assumed intangible liabilities:
Below-market leases			$ (108)
Below market lease, weighted average useful life			15 years