Investments in Unconsolidated Joint Ventures (Statements of Operations of the Joint Ventures) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015		Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Total revenue		$ 665,985	$ 618,476
Expenses
Depreciation and amortization		159,448	154,223
Total expenses		415,632	412,267
Operating income		250,353	206,209
Other expense
Interest expense		105,309	108,757
Net income		216,222	209,170
Income from unconsolidated joint ventures		1,791	14,834
Distribution related to excess loan proceeds		0	24,527
Mortgage loan		3,416,622			$ 3,435,242
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Total revenue	[1]	37,669	39,532
Expenses
Operating		16,667	16,275
Depreciation and amortization		9,064	9,071
Total expenses		25,731	25,346
Operating income		11,938	14,186
Other expense
Interest expense		8,389	7,980
Net income		3,549	6,206
Company's share of net income		1,599	14,642	[2]
Basis differential		192	192
Income from unconsolidated joint ventures		1,791	14,834
Straight-line rent adjustments		2,200	1,600
Mortgage loan		$ 829,089			$ 830,125
BP/CRF 901 New York Avenue LLC [Member]
Other expense
Distribution related to excess loan proceeds			24,500
Mortgage loan			$ 225,000

[1] Includes straight-line rent adjustments of approximately $2.2 million and $1.6 million for the three months ended March 31, 2016 and 2015, respectively.

[2] During the three months ended March 31, 2015, the Company received a distribution of approximately $24.5 million, which was generated from the excess loan proceeds from the refinancing of 901 New York Avenue’s mortgage loan to a new 10-year mortgage loan totaling $225.0 million. The Company’s allocation of income and distributions for the three months ended March 31, 2015 was not proportionate to its nominal ownership interest as a result of the achievement of specified investment return thresholds, as provided for in the joint venture agreement.