Real Estate Fund Investments - Schedule of Amounts Recognized in Income Statement (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Schedule Of Balance Sheet And Income Statement Items [Line Items]
Rental income	$ 143,243
Tenant reimbursement income	13,488
Fee and other income	4,495
Total revenues	161,226
Operating	61,884
Depreciation and amortization	73,583
General and administrative	12,613
Total expenses	148,080
Operating income	13,146
Unrealized gain on interest rate swaps	11,978
Interest and debt expense	(41,888)
Net income (loss) before income taxes	(10,853)
Income tax benefit (expense)	(574)
Net income (loss)	(11,427)
1633 Broadway [Member]
Schedule Of Balance Sheet And Income Statement Items [Line Items]
Rental income		35,719
Tenant reimbursement income		2,817
Fee and other income		522
Total revenues		39,058
Building operating		13,611
Related party management fees		701
Operating		14,312
Depreciation and amortization		2,787
Total expenses		17,099
Operating income		21,959
Unrealized gain on interest rate swaps		7,280
Interest and debt expense		(12,731)
Net income (loss) before income taxes		16,508
Net income (loss)		16,508
900 Third Avenue [Member]
Schedule Of Balance Sheet And Income Statement Items [Line Items]
Rental income		8,782
Tenant reimbursement income		763
Fee and other income		444
Total revenues		9,989
Building operating		4,045
Related party management fees		264
Operating		4,309
Depreciation and amortization		1,587
General and administrative		7
Total expenses		5,903
Operating income		4,086
Unrealized gain on interest rate swaps		1,766
Interest and debt expense		(3,657)
Net income (loss) before income taxes		2,195
Net income (loss)		2,195
31 West 52nd Street [Member]
Schedule Of Balance Sheet And Income Statement Items [Line Items]
Rental income		18,099
Tenant reimbursement income		1,189
Fee and other income		1,282
Total revenues		20,570
Building operating		5,743
Related party management fees		326
Operating		6,069
Depreciation and amortization		5,529
General and administrative		27
Total expenses		11,625
Operating income		8,945
Unrealized gain on interest rate swaps		2,602
Interest and debt expense		(5,505)
Net income (loss) before income taxes		6,042
Net income (loss)		6,042
1301 Avenue of the Americas [Member]
Schedule Of Balance Sheet And Income Statement Items [Line Items]
Rental income		26,610
Tenant reimbursement income		2,116
Fee and other income		570
Total revenues		29,296
Building operating		12,680
Related party management fees		410
Operating		13,090
Depreciation and amortization		9,214
General and administrative		27
Total expenses		22,331
Operating income		6,965
Unrealized gain on interest rate swaps		3,253
Interest and debt expense		(15,170)
Net income (loss) before income taxes		(4,952)
Net income (loss)		(4,952)
One Market Plaza [Member]
Schedule Of Balance Sheet And Income Statement Items [Line Items]
Rental income		18,213
Tenant reimbursement income		388
Fee and other income		1,363
Total revenues		19,964
Building operating		7,165
Related party management fees		217
Operating		7,382
Depreciation and amortization		9,004
General and administrative		13
Total expenses		16,399
Operating income		3,565
Unrealized gain on interest rate swaps		6,915
Interest and debt expense		(13,738)
Net income (loss) before income taxes		(3,258)
Net income (loss)		(3,258)
Liberty Place [Member]
Schedule Of Balance Sheet And Income Statement Items [Line Items]
Rental income		2,039
Tenant reimbursement income		621
Fee and other income		14
Total revenues		2,674
Building operating		1,082
Related party management fees		71
Operating		1,153
General and administrative		5
Total expenses		1,158
Operating income		1,516
Interest and debt expense		(945)
Unrealized depreciation on investment in real estate		(30)
Net income (loss) before income taxes		541
Income tax benefit (expense)		3
Net income (loss)		544
1899 Pennsylvania Avenue [Member]
Schedule Of Balance Sheet And Income Statement Items [Line Items]
Rental income		2,104
Tenant reimbursement income		1,140
Fee and other income		28
Total revenues		3,272
Building operating		1,257
Related party management fees		75
Operating		1,332
Depreciation and amortization		983
General and administrative		5
Total expenses		2,320
Operating income		952
Interest and debt expense		(1,128)
Net income (loss) before income taxes		(176)
Income tax benefit (expense)		68
Net income (loss)		(108)
2099 Pennsylvania Avenue [Member]
Schedule Of Balance Sheet And Income Statement Items [Line Items]
Rental income		33
Tenant reimbursement income		2
Fee and other income		3
Total revenues		38
Building operating		1,080
Related party management fees		1
Operating		1,081
General and administrative		387
Total expenses		1,468
Operating income		(1,430)
Interest and debt expense		(828)
Unrealized depreciation on investment in real estate		(10)
Net income (loss) before income taxes		(2,268)
Net income (loss)		(2,268)
425 Eye Street [Member]
Schedule Of Balance Sheet And Income Statement Items [Line Items]
Rental income		2,658
Tenant reimbursement income		744
Fee and other income		179
Total revenues		3,581
Building operating		1,514
Related party management fees		105
Operating		1,619
Depreciation and amortization		1,395
General and administrative		7
Total expenses		3,021
Operating income		560
Interest and debt expense		(1,219)
Net income (loss) before income taxes		(659)
Income tax benefit (expense)		(2,339)
Net income (loss)		$ (2,998)