Interest and Other Income, net - Schedule Of Interest And Other Income, net (Parenthetical) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Preferred equity investment income	$ 953	$ 1,423	$ 2,366	$ 2,839
Preferred equity ownership percentage	24.40%		24.40%
PGRESS Equity Holdings L.P. [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Preferred equity investment income	$ 232	$ 347	$ 576	$ 692
Preferred equity ownership percentage	24.40%		24.40%