Real Estate Investments (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($) ft² state	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) ft² site property state	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) ft² state
Real Estate Properties [Line Items]
Number of Real Estate Properties	789		789		645
Number of states | state	46		46		46
Land Subject to Ground Leases | ft²	14,000,000.0		14,000,000.0		11,200,000
Net Real Estate Investments	$ 2,118,928,000		$ 2,118,928,000		$ 1,661,334,000
Number of Development and Partner Capital Solutions Projects Construction	4		2
Number of properties sold	3		9
Proceeds from Sale of Real Estate	$ 7,700,000		$ 34,500,000
Gains (Losses) on Sales of Investment Real Estate	2,600,000		9,000,000.0
Impairment of Long-Lived Assets Held-for-use	0	$ 488,000	1,609,000	$ 1,651,000
Impaired Real Estate Estate Fair Value	3,000,000.0		3,000,000.0
Business Acquisition 2019 [Member]
Real Estate Properties [Line Items]
Payments to Acquire Property, Plant, and Equipment	$ 246,400,000		$ 565,000,000.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life (in year)	12 years 3 months 18 days		11 years 10 months 24 days
Retail Net Lease Assets Purchased	68		147
Number Of States Properties Located	27		37
Number of Contracts or Customers Comprising Ten Percent or More Of Company's Total Assets or Total Rent			0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Land	$ 165,200,000		$ 165,200,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Buildings	323,100,000		323,100,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	$ 76,700,000		$ 76,700,000