Joint Ventures - Unconsolidated JV - Sea Sound Apartments JV (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 31, 2020 USD ($)	Sep. 30, 2021 USD ($) item	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) item	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Investments
Outstanding debt		$ 198,880		$ 198,880		$ 161,418
Summarized financial information
Investment in real estate		647,874		647,874		551,653
Cash and cash equivalents		27,260	$ 102,351	27,260	$ 102,351	106,794
Other assets		69,897		69,897		65,866
Total assets		1,136,550		1,136,550		1,037,324
Debt, net		196,099		196,099		158,915
Other liabilities		91,758		91,758		72,035
Equity		598,618	552,420	598,618	552,420	568,170	$ 588,515	$ 542,650	$ 529,670
Total liabilities and equity		1,136,550		1,136,550		1,037,324
Revenues		53,996	42,041	167,540	96,695
Expenses:
Other operating expenses		4,987	5,113	17,161	16,975
Depreciation and amortization		4,617	3,303	12,594	9,394
Total expenses		37,835	31,016	115,090	75,890
Operating income (loss)		16,161	11,025	52,450	20,805
Interest expense		(4,114)	(3,379)	(11,639)	(10,113)
Net income		$ 14,777	$ 7,782	$ 41,759	$ 25,666
Sea Sound Apartments JV
Investments
Value of land contributed	$ 5,100
Mitigation bank credits contributed						400
Cash contributed						4,900
Cash contributed by JV partner						$ 6,900
Ownership percentage		60.00%		60.00%		60.00%
Unconsolidated joint ventures
Investments
Outstanding debt		$ 66,583		$ 66,583		$ 33,088
Sea Sound Apartments JV
Investments
Outstanding debt		31,833		31,833		8,789
Summarized financial information
Investment in real estate		52,055		52,055		29,085
Cash and cash equivalents		172		172		15
Other assets		30		30
Total assets		52,257		52,257		29,100
Debt, net		31,570		31,570		8,378
Other liabilities		3,578		3,578		3,439
Equity		17,109		17,109		17,283
Total liabilities and equity		52,257		52,257		29,100
Revenues		143		164
Expenses:
Cost of revenue		142		213
Other operating expenses		16		16
Depreciation and amortization		72		72
Total expenses		230		301
Operating income (loss)		(87)		(137)
Interest expense		(37)		(37)
Net income		(124)		(174)
Sea Sound Apartments JV | Sea Sound Apartments JV Loan
Investments
Loan amount	$ 40,300
Outstanding debt		$ 31,800		$ 31,800		$ 8,800
Sea Sound Apartments JV | LIBOR | Sea Sound Apartments JV Loan
Investments
Basis spread on variable rate (as a percent)	2.15%
Sea Sound Apartments JV | Apartment
Investments
Number of units remaining to be developed and constructed | item		218		218
Number of units to be developed | item		300		300