Investments - Share of Earnings and Losses of Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Equity Method Investments [Roll Forward]
Balance as of December 31, 2018	$ 30,565
Net income	1,619
Distributions	(14,013)
Other comprehensive loss	(217)	$ 122	$ 465
Impairment	(6,926)
Balance as of December 31, 2019	11,028	30,565
Digital Realty Joint Venture
Equity Method Investments [Roll Forward]
Balance as of December 31, 2018	27,291
Net income	(2,509)
Distributions	(7,055)
Other comprehensive loss	(217)
Impairment	(6,926)
Balance as of December 31, 2019	10,584	27,291
Heritage Common X
Equity Method Investments [Roll Forward]
Balance as of December 31, 2018	3,274
Net income	4,128
Distributions	(6,958)
Other comprehensive loss	0
Impairment	0
Balance as of December 31, 2019	444	$ 3,274
Disposition and advisory fees	600
Fees and taxes incurred	$ 1,200