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Summary of Significant Accounting Policies - Narrative (Details)
Mar. 31, 2015
Minimum [Member]  
Accounting Policies [Line Items]  
Percent of observatory revenue in quarter one over a ten year period 16.00%esrt_HistoricalRevenueTrendObservatoryRevenueinQuarterOneOverTenYearPeriodPercent
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
Percent of observatory revenue in quarter two over a ten year period 26.00%esrt_HistoricalRevenueTrendObservatoryRevenueinQuarterTwoOverTenYearPeriodPercent
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
Percent of observatory revenue in quarter three over a ten year period 31.00%esrt_HistoricalRevenueTrendObservatoryRevenueinQuarterThreeOverTenYearPeriodPercent
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
Percent of observatory revenue in quarter four over a ten year period 23.00%esrt_HistoricalRevenueTrendObservatoryRevenueinQuarterFourOverTenYearPeriodPercent
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
Maximum [Member]  
Accounting Policies [Line Items]  
Percent of observatory revenue in quarter one over a ten year period 18.00%esrt_HistoricalRevenueTrendObservatoryRevenueinQuarterOneOverTenYearPeriodPercent
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
Percent of observatory revenue in quarter two over a ten year period 28.00%esrt_HistoricalRevenueTrendObservatoryRevenueinQuarterTwoOverTenYearPeriodPercent
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
Percent of observatory revenue in quarter three over a ten year period 33.00%esrt_HistoricalRevenueTrendObservatoryRevenueinQuarterThreeOverTenYearPeriodPercent
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
Percent of observatory revenue in quarter four over a ten year period 25.00%esrt_HistoricalRevenueTrendObservatoryRevenueinQuarterFourOverTenYearPeriodPercent
/ us-gaap_RangeAxis
= us-gaap_MaximumMember