Real Estate Joint Ventures - Summarized Statements of Operations for Unconsolidated Investments (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Investments in and Advances to Affiliates [Line Items]
Operating revenue	$ 18,747	$ 27,192	$ 29,551	$ 20,254	$ 21,104	$ 27,830	$ 37,846	$ 17,091	$ 95,744	$ 103,871	$ 701,873
Total expenses									93,784	110,006	188,623
Net loss									(15,464)	1,971	(406,282)
Statements Of Operations
Investments in and Advances to Affiliates [Line Items]
Operating revenue									371	0	5
Total expenses									1,159	3,073	1,957
Net loss									788	$ 3,073	$ 1,952
Artisan Park, L.L.C | Consolidated Variable Interest Entities
Investments in and Advances to Affiliates [Line Items]
Operating revenue									$ 400