Partners' Capital of the Operating Partnership - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended			12 Months Ended
	Aug. 15, 2017	Mar. 30, 2017	Jan. 31, 2017	Aug. 31, 2012	Mar. 31, 2012	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Class of Stock [Line Items]
Original issuance costs of redeemed preferred units						$ 0	$ 7,589	$ 0
Common stock, shares issued (in shares)			4,427,500
Aggregate net proceeds after selling commissions			$ 308,800			$ 130,693	$ 326,058	$ 31,117
Common stock, par value (in dollars per share)						$ 0.01
Brannan St Project [Member]
Class of Stock [Line Items]
Business acquisition, equity interest issued or issuable (in shares)							867,701
Share price (in dollars per share)									$ 55.36
Common stock, par value (in dollars per share)									$ 0.01
Series H Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock (in shares)	4,000,000
Preferred stock, dividend rate	6.375%			6.375%
Series G Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock (in shares)		4,000,000
Preferred stock, dividend rate		6.875%			6.875%