Equity - Additional Information (Details) - USD ($)										1 Months Ended	3 Months Ended				6 Months Ended		12 Months Ended
	Aug. 05, 2020	Jul. 30, 2020	Jul. 15, 2020	Apr. 15, 2020	Apr. 02, 2020	Mar. 10, 2020	Jan. 15, 2020	Jan. 02, 2020	Aug. 06, 2019	Jul. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Jul. 02, 2020
Class of Stock
Preferred stock, shares authorized (in shares)											100,000,000				100,000,000		100,000,000
Net proceeds from issuance of common and preferred stock											$ 4,416,000	$ 1,349,000	$ 7,498,000	$ 30,206,000
Preferred stock, par value (in dollars per share)											$ 0.01				$ 0.01		$ 0.01
Percentage of operating partnership held											72.80%				72.80%		72.60%
Acquisition of noncontrolling interest in real estate entity											$ (6,130,000)
Aggregate cash dividends and distributions, paid															$ 35,549,000	$ 28,003,000
Dividends and distributions declared per common share and unit (in dollars per share)												$ 0.22	$ 0.21	$ 0.21
Class A units
Class of Stock
Class A Units not held by Company (in shares)											21,272,962				21,272,962
Class A units | Operating Partnership
Class of Stock
Aggregate cash dividends and distributions, paid					$ 4,700,000			$ 4,500,000
Additional paid-in capital
Class of Stock
Net proceeds from issuance of common and preferred stock											$ 4,411,000	$ 1,348,000	$ 7,494,000	$ 30,185,000
Acquisition of noncontrolling interest in real estate entity											(2,386,000)
Common stock
Class of Stock
Net proceeds from issuance of common and preferred stock											$ 5,000	1,000	4,000	$ 21,000
Aggregate cash dividends and distributions, paid					$ 12,400,000			$ 11,800,000
New ATM Program | Common stock
Class of Stock
Maximum aggregate offering price of shares to be sold (up to)									$ 180,700,000
The Amendments
Class of Stock
Consideration received on transaction												$ 1,700,000
The Amendments | Common stock
Class of Stock
Shares issued (in shares)												92,577			486,727
Weighted average price (in dollars per share)											$ 9.28	$ 18.23			$ 9.28
Consideration received on transaction															$ 4,400,000
Noncontrolling interests in investment entities
Class of Stock
Liquidation preference											$ 63,300,000				63,300,000
Noncontrolling interests in investment entities | Operating Partnership
Class of Stock
Ownership interest percentage in properties											$ 600,000				$ 600,000
Consolidated Entities Under Development Or Construction | Operating Partnership
Class of Stock
Ownership interest percentage in properties																	$ 4,500,000
Redeemable convertible preferred stock
Class of Stock
Preferred stock, shares authorized (in shares)											2,930,000				2,930,000		2,930,000
Net proceeds from issuance of common and preferred stock											$ 91,000		61,001,000
Preferred Stock dividend rate percentage															6.75%		6.75%
Aggregate cash dividends and distributions, paid				$ 1,100,000			$ 1,100,000
Redeemable convertible preferred stock | Additional paid-in capital
Class of Stock
Net proceeds from issuance of common and preferred stock											(5,000)		(2,249,000)
Redeemable convertible preferred stock | Preferred stock
Class of Stock
Net proceeds from issuance of common and preferred stock											$ 96,000		$ 63,250,000
Redeemable convertible preferred stock | At The Market Program
Class of Stock
Maximum aggregate offering price of shares to be sold (up to)						$ 300,000,000.0
Preferred Stock dividend rate percentage						6.75%
Series A Preferred Stock | The Amendments
Class of Stock
Shares issued (in shares)															3,830
Weighted average price (in dollars per share)											$ 24.14				$ 24.14
Consideration received on transaction															$ 100,000
1405 Point
Class of Stock
Percentage of voting interests acquired											21.00%				21.00%
Notes payable											$ 6,100,000				$ 6,100,000
Remaining lease term											42 years				42 years
1405 Point | Additional paid-in capital
Class of Stock
Acquisition of noncontrolling interest in real estate entity											$ 2,400,000
Construction loans
Class of Stock
Borrowings under construction loans															$ 31,600,000
Subsequent Event | At The Market Program
Class of Stock
Consideration received on transaction										$ 1,700,000
Subsequent Event | Common stock
Class of Stock
Dividends and distributions declared per common share and unit (in dollars per share)		$ 0.11
Subsequent Event | Redeemable convertible preferred stock
Class of Stock
Preferred stock, shares authorized (in shares)																		6,380,000
Aggregate cash dividends and distributions, paid			$ 1,200,000
Subsequent Event | Redeemable convertible preferred stock | Preferred stock
Class of Stock
Preferred stock, dividends declared (in dollars per share)		$ 0.421875
Subsequent Event | Series A Preferred Stock | The Amendments
Class of Stock
Maximum aggregate offering price of shares to be sold (up to)	$ 277,500,000
Subsequent Event | Series A Preferred Stock | At The Market Program
Class of Stock
Consideration received on transaction										16,000,000.0
Subsequent Event | Construction loans
Class of Stock
Borrowings under construction loans										$ 2,900,000