Segment Reporting Reportable Segments (Details) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014 segment		Jun. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Revenues	$ 155,168,000		$ 59,569,000		$ 295,474,000		$ 121,989,000
Interest expense	(14,629,000)				(28,966,000)
Depreciation, Depletion and Amortization, Nonproduction	(28,637,000)				(58,752,000)
Income (Loss) from Equity Method Investments	0		7,898,000		0		7,898,000
Net Income (Loss) Attributable to Parent	9,834,000				14,203,000
Assets	2,476,625,000				2,476,625,000			2,476,061,000
Equity Method Investments	0		82,515,000		0		82,515,000		76,879,000
Number of reportable segments					2
Real Estate, Segment [Member]
Segment Reporting Information [Line Items]
Revenues	110,838,000		53,303,000		218,865,000		109,478,000
Operating Expenses, Excluding Noncash Items	(63,380,000)		(20,141,000)		(128,942,000)		(41,745,000)
Interest expense	(14,629,000)		(14,715,000)		(28,966,000)		(28,911,000)
Depreciation, Depletion and Amortization, Nonproduction	(28,556,000)		(13,118,000)		(58,607,000)		(25,267,000)
Income (Loss) from Equity Method Investments			6,079,000				7,898,000
Assets	2,221,530,000		999,902,000		2,221,530,000		999,902,000
Equity Method Investments			82,515,000				82,515,000
Payments to Acquire Productive Assets	37,735,000		19,968,000		54,978,000		33,011,000
Observatory, Segment [Member] [Member]
Segment Reporting Information [Line Items]
Revenues	30,389,000				47,690,000
Operating Expenses, Excluding Noncash Items	(25,799,000)				(45,845,000)
Interest expense	0				0
Depreciation, Depletion and Amortization, Nonproduction	(77,000)				(138,000)
Assets	243,189,000				243,189,000
Payments to Acquire Productive Assets	0				0
Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	12,966,000		6,218,000		27,944,000		12,400,000
Operating Expenses, Excluding Noncash Items	(13,591,000)		(8,269,000)		(28,706,000)		(17,028,000)
Interest expense	0		0		0		0
Depreciation, Depletion and Amortization, Nonproduction	(4,000)		7,000		(7,000)		0
Income (Loss) from Equity Method Investments			0				0
Assets	11,906,000		11,356,000		11,906,000		11,356,000
Equity Method Investments			0				0
Payments to Acquire Productive Assets	0		0		0		0
Total, Segment [Member]
Segment Reporting Information [Line Items]
Revenues	154,193,000		59,521,000		294,499,000		121,878,000
Operating Expenses, Excluding Noncash Items	(102,770,000)		(28,410,000)		(203,493,000)		(58,773,000)
Interest expense	(14,629,000)		(14,715,000)		(28,966,000)		(28,911,000)
Depreciation, Depletion and Amortization, Nonproduction	(28,637,000)		(13,111,000)		(58,752,000)		(25,267,000)
Income (Loss) from Equity Method Investments			6,079,000				7,898,000
Assets	2,476,625,000		1,011,258,000		2,476,625,000		1,011,258,000
Equity Method Investments			82,515,000				82,515,000
Payments to Acquire Productive Assets	37,735,000		19,968,000		54,978,000		33,011,000
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(17,199,000)		(2,053,000)		(33,429,000)		(4,844,000)
Intersegment Eliminations [Member] | Real Estate, Segment [Member]
Segment Reporting Information [Line Items]
Revenues	16,298,000	[1]	19,000	[1]	31,566,000	[1]	37,000
Intersegment Eliminations [Member] | Observatory, Segment [Member] [Member]
Segment Reporting Information [Line Items]
Revenues	0				0
Intersegment Eliminations [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	901,000		2,034,000		1,863,000		4,807,000
Intersegment Eliminations [Member] | Total, Segment [Member]
Segment Reporting Information [Line Items]
Revenues	17,199,000		2,053,000		33,429,000		4,844,000
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	171,392,000		61,574,000		327,928,000		126,722,000
Operating Segments [Member] | Real Estate, Segment [Member]
Segment Reporting Information [Line Items]
Revenues	127,136,000		53,322,000		250,431,000		109,515,000
Net Income (Loss) Attributable to Parent	20,571,000		11,427,000		33,916,000		21,490,000
Operating Segments [Member] | Observatory, Segment [Member] [Member]
Segment Reporting Information [Line Items]
Revenues	30,389,000				47,690,000
Net Income (Loss) Attributable to Parent	4,513,000				1,707,000
Operating Segments [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	13,867,000		8,252,000		29,807,000		17,207,000
Net Income (Loss) Attributable to Parent	272,000		(10,000)		1,094,000		179,000
Operating Segments [Member] | Total, Segment [Member]
Segment Reporting Information [Line Items]
Revenues	171,392,000		61,574,000		327,928,000		126,722,000
Net Income (Loss) Attributable to Parent	$ 25,356,000		$ 11,417,000		$ 36,717,000		$ 21,669,000

[1] The observatory pays a market-based rent payment comprised of fixed and percentage rent to the Empire State Building.