Equity - Additional Information (Details)											1 Months Ended	3 Months Ended				6 Months Ended
	Jul. 03, 2019 USD ($)	Jul. 01, 2019 shares	Jun. 18, 2019 USD ($) ft² $ / shares shares	May 30, 2019 USD ($) shares	May 23, 2019 USD ($) shares	May 07, 2019 $ / shares	Apr. 04, 2019 USD ($)	Jan. 03, 2019 USD ($)	Jan. 02, 2019 shares	Feb. 26, 2018 USD ($)	Jul. 31, 2019 USD ($) $ / shares shares	Jun. 30, 2019 USD ($) $ / shares shares	Mar. 31, 2019 $ / shares	Jun. 30, 2018 $ / shares	Mar. 31, 2018 $ / shares	Jun. 30, 2019 USD ($) $ / shares shares	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) $ / shares shares
Class of Stock
Preferred stock issued (in shares) | shares												2,530,000				2,530,000		0
Preferred stock, par value (in dollars per share) | $ / shares												$ 0.01				$ 0.01		$ 0.01
Percentage of Operating Partnership held												71.40%				71.40%		74.50%
Aggregate cash dividends and distributions, paid																$ 28,003,000	$ 24,337,000
Dividends and distributions declared per common share and unit (in dollars per share) | $ / shares						$ 0.21						$ 0.20	$ 0.21	$ 0.21	$ 0.20
Class A units
Class of Stock
Class A Units not held by Company (in shares) | shares												21,177,692				21,177,692
Class A units | Operating Partnership
Class of Stock
Number of shares issued (in shares) | shares				60,000	4,125,759
Business acquisition, equity interest issued or issuable, value assigned				$ 1,000,000.0	$ 68,100,000
Business acquisition, percentage of voting interests acquired				35.00%
Aggregate cash dividends and distributions, paid							$ 3,600,000	$ 3,400,000
Common stock
Class of Stock
Shares issued (in shares) | shares									118,471
Aggregate cash dividends and distributions, paid							$ 11,000,000.0	$ 10,000,000.0
New ATM Program
Class of Stock
Consideration received on transaction																$ 37,800,000
New ATM Program | Common stock
Class of Stock
Maximum aggregate offering price of shares to be sold (up to)										$ 125,000,000.0
Shares issued (in shares) | shares																2,522,186
Weighted average price (in dollars per share) | $ / shares												$ 15.16				$ 15.16
Subsequent Event | Class A units | Operating Partnership
Class of Stock
Aggregate cash dividends and distributions, paid	$ 4,400,000
Subsequent Event | Common stock
Class of Stock
Aggregate cash dividends and distributions, paid	$ 11,100,000
Subsequent Event | New ATM Program
Class of Stock
Consideration received on transaction											$ 1,000,000.0
Subsequent Event | New ATM Program | Common stock
Class of Stock
Shares issued (in shares) | shares											62,823
Weighted average price (in dollars per share) | $ / shares											$ 16.84
Noncontrolling interests in investment entities
Class of Stock
Liquidation preference												$ 63,300,000				$ 63,300,000
Consolidated Entities Under Development Or Construction | Operating Partnership
Class of Stock
Ownership interest percentage in properties												$ 0				$ 0		$ 0
Redeemable convertible preferred stock
Class of Stock
Preferred stock issued (in shares) | shares			2,530,000
Preferred Stock dividend rate percentage			6.75%													6.75%
Preferred stock, dividends, not yet paid (in dollars per share) | $ / shares																$ 0.0609
Preferred stock, par value (in dollars per share) | $ / shares			$ 0.01
Preferred stock, liquidation preference (in dollars per share) | $ / shares			$ 25.00
Proceeds from issuance of preferred stock			$ 61,300,000
Preferred stock, redemption price (in usd per unit) | $ / shares												$ 25.00				$ 25.00
Redeemable convertible preferred stock | Over-Allotment Option
Class of Stock
Preferred stock issued (in shares) | shares			330,000
Series A Cumulative Redeemable Perpetual Preferred Units
Class of Stock
Preferred stock issued (in shares) | shares			2,530,000
Preferred Stock dividend rate percentage			6.75%
Class A Units | Subsequent Event | Common stock
Class of Stock
Shares issued (in shares) | shares		125,118
Thames Street Wharf
Class of Stock
Area of Real Estate Property | ft²			263,426
1405 Point | Noncontrolling interests in investment entities | Operating Partnership
Class of Stock
Ownership interest percentage in properties												$ 4,600,000				$ 4,600,000