Property Acquisitions and Dispositions - Acquisitions of Operating Stores (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($) store shares	Sep. 30, 2019 USD ($) store shares	Jun. 30, 2019 USD ($) store shares	Mar. 31, 2019 USD ($) store shares	Dec. 31, 2018 USD ($) store shares	Sep. 30, 2018 USD ($) store shares	Jun. 30, 2018 USD ($) store shares	Mar. 31, 2018 USD ($) store shares	Dec. 31, 2019 USD ($) store shares	Dec. 31, 2018 USD ($) store shares	Dec. 31, 2017 USD ($)
Real Estate [Abstract]
Number of Stores | store	5	1	1	14	6	6	17	5	21	34
Total Real Estate Assets Acquired	$ 51,278	$ 16,937	$ 8,424	$ 223,740	$ 74,852	$ 74,694	$ 237,284	$ 70,787	$ 300,379	$ 457,617
Cash Paid	51,058	16,941	8,424	202,890	74,868	71,989	148,650	70,171	279,313	365,678
Loan Assumed	0	0	0	17,157	0	0	87,500	0	17,157	87,500	$ 24,055
Investments in Real Estate Ventures	0	0	0	2,780	0	0	(1,024)	489	2,780	(535)	$ 12,957
Net Liabilities/ (Assets) Assumed	220	(4)	0	913	(16)	2,705	281	127	1,129	3,097
Value of OP Units Issued	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 1,877	$ 0	$ 0	$ 1,877
Number of OP Units Issued (in shares) | shares	0	0	0	0	0	0	21,768	0	0	21,768
Number of stores acquired, previously held noncontrolling interest | store									12	15