Investments in Unconsolidated Joint Ventures (Statements of Operations of the Joint Ventures) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Total revenue		$ 632,228	$ 665,985
Expenses
Depreciation and amortization		159,205	159,448
Total expenses		426,003	415,632
Operating income		206,225	250,353
Other expense
Interest expense		95,534	105,309
Net income		115,564	216,222
Income from unconsolidated joint ventures		3,084	1,791
Mortgage notes payable, net		2,046,959		$ 2,063,087
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Total revenue	[1]	54,761	37,669
Expenses
Operating		22,079	16,667
Depreciation and amortization		14,309	9,064
Total expenses		36,388	25,731
Operating income		18,373	11,938
Other expense
Interest expense		9,300	8,389
Net income		9,073	3,549
Company's share of net income		4,323	1,599
Basis differential	[2]	(1,239)	192
Income from unconsolidated joint ventures		3,084	1,791
Straight-line rent adjustments		7,000	$ 2,200
Mortgage notes payable, net		864,344		$ 865,665
Colorado Center [Member]
Other expense
Straight-line rent adjustments		700
"Above" and "below" market rent adjustments, net		$ 400

[1] Includes straight-line rent adjustments of approximately $7.0 million and $2.2 million for the three months ended March 31, 2017 and 2016, respectively.

[2] Includes a straight-line rent adjustment of approximately $0.7 million and a net above-/below-market rent adjustment of approximately $0.4 million for the three months ended March 31, 2017.