Investment In Unconsolidated Joint Ventures (Summary of Financial Information for Joint Ventures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Sep. 09, 2014	Sep. 27, 2013
Schedule of Equity Method Investments [Line Items]
Net Investment in Properties	$ 758,582	$ 779,752	$ 584,837
Total Assets	935,990	942,107	676,015
Mortgage Loans	460,023	461,548	337,953
Total Liabilities	558,310	569,895	444,062
Equity / (Deficit)	377,679	372,212	231,953
Investment in and share of equity	106,107	94,729	70,504
Revenues	129,649	102,303	54,770
Property Operating Expense	(36,146)	(26,873)	(17,027)
Net Operating Income	93,503	75,430	37,743
Net Income (Loss)	37,350	30,577	20,651
Investment in and share of net income (loss)	$ 15,491	$ 13,289	$ 9,796
2001 Sixth Avenue
Schedule of Equity Method Investments [Line Items]
% Ownership	50.00%	50.00%	50.00%
Net Investment in Properties	$ 33,757	$ 37,620	$ 33,980
Total Assets	44,732	42,537	39,674
Mortgage Loans	102,998	104,523	105,953
Total Liabilities	107,807	110,749	111,943
Equity / (Deficit)	(63,075)	(68,212)	(72,269)
Revenues	43,734	39,807	37,625
Property Operating Expense	(15,205)	(14,707)	(11,981)
Net Operating Income	28,529	25,100	25,644
Net Income (Loss)	$ 14,171	$ 11,982	$ 12,346
700/750 Central Expressway
Schedule of Equity Method Investments [Line Items]
% Ownership			50.00%
Net Investment in Properties			$ 0
Total Assets			0
Mortgage Loans			0
Total Liabilities			0
Equity / (Deficit)			0
Revenues			55
Property Operating Expense			(1)
Net Operating Income			54
Net Income (Loss)			$ 58
2020 Fifth Avenue
Schedule of Equity Method Investments [Line Items]
% Ownership	50.00%	50.00%	50.00%
Net Investment in Properties	$ 46,633	$ 47,239	$ 47,901
Total Assets	55,257	55,123	53,389
Mortgage Loans	47,000	47,000	47,000
Total Liabilities	47,857	47,795	47,525
Equity / (Deficit)	7,400	7,328	5,864
Revenues	8,474	8,308	7,513
Property Operating Expense	(1,177)	(1,086)	(522)
Net Operating Income	7,297	7,222	6,991
Net Income (Loss)	$ 4,840	$ 4,844	$ 5,756
33 Chun Choi Street (Hong Kong)
Schedule of Equity Method Investments [Line Items]
% Ownership	50.00%	50.00%	50.00%
Net Investment in Properties	$ 138,742	$ 143,014	$ 102,428
Total Assets	179,525	165,912	122,890
Mortgage Loans	0	0	0
Total Liabilities	4,173	10,210	8,382
Equity / (Deficit)	175,352	155,702	114,508
Revenues	17,700	8,671	0
Property Operating Expense	(5,358)	(2,625)	(44)
Net Operating Income	12,342	6,046	(44)
Net Income (Loss)	$ 4,480	$ 2,976	$ (150)
PREI ®
Schedule of Equity Method Investments [Line Items]
% Ownership	20.00%	20.00%			20.00%
Net Investment in Properties	$ 419,498	$ 429,358
Total Assets	481,175	492,494
Mortgage Loans	208,000	208,000
Total Liabilities	293,276	296,480
Equity / (Deficit)	187,898	196,014
Revenues	40,011	39,467
Property Operating Expense	(6,157)	(6,144)
Net Operating Income	33,854	33,323
Net Income (Loss)	$ 15,121	$ 12,378
GCEAR
Schedule of Equity Method Investments [Line Items]
% Ownership	20.00%	20.00%		20.00%
Net Investment in Properties	$ 119,952	$ 122,521
Total Assets	175,301	186,041
Mortgage Loans	102,025	102,025
Total Liabilities	105,197	104,661
Equity / (Deficit)	70,104	81,380
Revenues	19,730	6,050
Property Operating Expense	(8,249)	(2,311)
Net Operating Income	11,481	3,739
Net Income (Loss)	$ (1,262)	$ (1,603)