Real Estate Fund Investments - Schedule of Amounts Recognized in Income Statement (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended				11 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Nov. 23, 2014	Dec. 31, 2015	Dec. 31, 2013
Real Estate Properties [Line Items]
Rental income	$ 57,465						$ 586,530
Tenant reimbursement income	5,865						50,885
Fee and other income	2,805						24,993
Total revenues	66,135	$ 170,528	$ 167,726	$ 162,928	$ 161,226		662,408
Operating	26,011						244,754
Depreciation and amortization	34,481						294,624
General and administrative	2,207						42,056
Total expenses	62,699						591,789
Operating income (loss)	3,436						70,619
Unrealized gain on interest rate swaps	15,084						75,760
Interest and debt expense	(43,743)						(168,366)
Net income before income taxes	73,227						23,709
Income tax expense	(505)						(2,566)
Net income	$ 72,722						$ 21,143
1633 Broadway [Member]
Real Estate Properties [Line Items]
Rental income						$ 136,422		$ 130,590
Tenant reimbursement income						12,742		13,538
Fee and other income						2,951		2,994
Total revenues						152,115		147,122
Building operating						50,830		54,867
Related party management fees						2,864		2,870
Operating						53,694		57,737
Depreciation and amortization						10,990		11,187
General and administrative						118		251
Total expenses						64,802		69,175
Operating income (loss)						87,313		77,947
Unrealized gain on interest rate swaps						25,226		34,711
Interest and debt expense						(46,315)		(52,563)
Net income before income taxes						66,224		60,095
Net income						66,224		60,095
900 Third Avenue [Member]
Real Estate Properties [Line Items]
Rental income						31,219		33,601
Tenant reimbursement income						3,001		3,036
Fee and other income						1,680		732
Total revenues						35,900		37,369
Building operating						14,904		16,150
Related party management fees						914		980
Operating						15,818		17,130
Depreciation and amortization						6,085		6,349
General and administrative						113		156
Total expenses						22,016		23,635
Operating income (loss)						13,884		13,734
Unrealized gain on interest rate swaps						5,759		9,985
Interest and debt expense						(13,269)		(14,872)
Net income before income taxes						6,374		8,847
Net income						6,374		8,847
31 West 52nd Street [Member]
Real Estate Properties [Line Items]
Rental income						67,453		77,257
Tenant reimbursement income						5,126		5,100
Fee and other income						3,360		1,154
Total revenues						75,939		83,511
Building operating						21,516		22,905
Related party management fees						1,244		1,295
Operating						22,760		24,200
Depreciation and amortization						23,438		22,688
General and administrative						119		130
Total expenses						46,317		47,018
Operating income (loss)						29,622		36,493
Unrealized gain on interest rate swaps						8,466		15,993
Interest and debt expense						(20,092)		(22,307)
Net income before income taxes						17,996		30,179
Net income						17,996		30,179
1301 Avenue of the Americas [Member]
Real Estate Properties [Line Items]
Rental income						104,220		97,576
Tenant reimbursement income						8,252		9,693
Fee and other income						9,667		2,598
Total revenues						122,139		109,867
Building operating						46,679		51,247
Related party management fees						1,580		1,646
Operating						48,259		52,893
Depreciation and amortization						37,212		37,075
General and administrative						167		215
Total expenses						85,638		90,183
Operating income (loss)						36,501		19,684
Unrealized gain on interest rate swaps						12,042		21,275
Interest and debt expense						(54,436)		(68,540)
Net income before income taxes						(5,893)		(27,581)
Net income						(5,893)		(27,581)
One Market Plaza [Member]
Real Estate Properties [Line Items]
Rental income						65,314		77,265
Tenant reimbursement income						1,191		1,707
Fee and other income						3,242		7,778
Total revenues						69,747		86,750
Building operating						25,119		29,985
Related party management fees						701		832
Operating						25,820		30,817
Depreciation and amortization						31,422		37,847
General and administrative						4,545		236
Total expenses						61,787		68,900
Operating income (loss)						7,960		17,850
Unrealized gain on interest rate swaps						20,848		36,378
Interest and debt expense						(48,486)		(55,170)
Net income before income taxes						(19,678)		(942)
Net income						(19,678)		(942)
Liberty Place [Member]
Real Estate Properties [Line Items]
Rental income						5,823		8,421
Tenant reimbursement income						1,884		2,528
Fee and other income						50		82
Total revenues						7,757		11,031
Building operating						3,911		4,286
Related party management fees						214		275
Operating						4,125		4,561
General and administrative						66		63
Total expenses						4,191		4,624
Operating income (loss)						3,566		6,407
Interest and debt expense						(3,488)		(3,887)
Unrealized (depreciation) appreciation on investment in real estate						(2,772)		(2,066)
Net income before income taxes						(2,694)		454
Income tax expense						(105)		(45)
Net income						(2,799)		409
1899 Pennsylvania Avenue [Member]
Real Estate Properties [Line Items]
Rental income						7,249		9,686
Tenant reimbursement income						3,648		4,807
Fee and other income						115		153
Total revenues						11,012		14,646
Building operating						4,674		5,066
Related party management fees						254		330
Operating						4,928		5,396
Depreciation and amortization						3,484		4,139
General and administrative						58		69
Total expenses						8,470		9,604
Operating income (loss)						2,542		5,042
Interest and debt expense						(4,051)		(4,514)
Net income before income taxes						(1,509)		528
Income tax expense						53		(54)
Net income						(1,456)		474
2099 Pennsylvania Avenue [Member]
Real Estate Properties [Line Items]
Rental income						165		432
Tenant reimbursement income						6		74
Fee and other income						280		58
Total revenues						451		564
Building operating						4,147		4,531
Related party management fees						38		13
Operating						4,185		4,544
General and administrative						798		66
Total expenses						4,983		4,610
Operating income (loss)						(4,532)		(4,046)
Unrealized gain on interest rate swaps								1,101
Interest and debt expense						(4,578)		(5,285)
Unrealized (depreciation) appreciation on investment in real estate						(749)		1,965
Net income before income taxes						(9,859)		(6,265)
Net income						(9,859)		(6,265)
425 Eye Street [Member]
Real Estate Properties [Line Items]
Rental income						9,501		10,167
Tenant reimbursement income						879		4
Fee and other income						319		801
Total revenues						10,699		10,972
Building operating						5,148		5,448
Related party management fees						339		354
Operating						5,487		5,802
Depreciation and amortization						5,022		5,502
General and administrative						71		75
Total expenses						10,580		11,379
Operating income (loss)						119		(407)
Unrealized gain on interest rate swaps								427
Interest and debt expense						(4,548)		(5,664)
Net income before income taxes						(4,429)		(5,644)
Income tax expense						(2,430)		2,492
Net income						$ (6,859)		$ (3,152)