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Stock Option and Incentive Plan Stock Option and Incentive Plan (Narrative) (Details) (USD $)
 0 Months Ended
Jan. 21, 2015
tiers
indices
Y
Feb. 06, 2015
2015 MYLTIP [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
TRS Measurement, Years 3bxp_TrsMeasurementYears
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_MYLTIPtwothousandfifteenMember		  
Indices Used to Compare TRS 2bxp_IndicesUsedToCompareTrs
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_MYLTIPtwothousandfifteenMember		  
Number of Tiers 3bxp_NumberOfTiers
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_MYLTIPtwothousandfifteenMember		  
Percentage of annualized TRS for Reduction of Earned Awards 0.00%bxp_PercentageOfAnnualizedTrsForReductionOfEarnedAwards
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_MYLTIPtwothousandfifteenMember		  
Percentage to Cause Some Awards to be Earned Even if on a Relative Basis it Would Not Result in any Earned Awards 12.00%bxp_PercentageToCauseSomeAwardsToBeEarnedEvenIfOnRelativeBasisItWouldNotResultInAnyEarnedAwards
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_MYLTIPtwothousandfifteenMember		  
Distributions Percent Before Measurement Date 10.00%bxp_DistributionsPercentBeforeMeasurementDate
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_MYLTIPtwothousandfifteenMember		  
Value of MYLTIP Awards $ 15,700,000bxp_ValueOfMyltipAwards
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_MYLTIPtwothousandfifteenMember		  
MYLTIP Value Amortized Into Earnings, Years 4bxp_MyltipValueAmortizedIntoEarningsYears
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_MYLTIPtwothousandfifteenMember		  
OPP Units 2012 [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Potential Awards Earned   40,000,000bxp_PotentialAwardsEarned
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_OppUnitsTwoThousandAndTwelveMember
Outperformance awards earned   32,100,000bxp_Outperformanceawardsearned
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_OppUnitsTwoThousandAndTwelveMember
Potential maximum amount of Outperformance Awards earned (percent)   80.00%bxp_PotentialmaximumamountofOutperformanceAwardsearnedpercent
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_OppUnitsTwoThousandAndTwelveMember
2012 OPP Units Forfeited (in shares)   174,549bxp_TwoThousandTwelveOPPUnitsForfeited
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_OppUnitsTwoThousandAndTwelveMember
Cohen & Steers Realty Majors Portfolio Index [Member] | 2015 MYLTIP [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Weighted Percentage of Index Used to Compare to TRS 50.00%bxp_WeightedPercentageOfIndexUsedToCompareToTrs
/ bxp_PerformanceIndexAxis
= bxp_CohenSteersRealtyMajorsPortfolioIndexMember
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_MYLTIPtwothousandfifteenMember		  
NAREIT Office Index adjusted [Member] | 2015 MYLTIP [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Weighted Percentage of Index Used to Compare to TRS 50.00%bxp_WeightedPercentageOfIndexUsedToCompareToTrs
/ bxp_PerformanceIndexAxis
= bxp_NareitOfficeIndexAdjustedMember
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_MYLTIPtwothousandfifteenMember		  
Target [Member] | 2015 MYLTIP [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Amount of Each Tier 16,300,000bxp_AmountOfEachTier
/ us-gaap_RangeAxis
= bxp_TargetMember
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_MYLTIPtwothousandfifteenMember		  
Threshold [Member] | 2015 MYLTIP [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Amount of Each Tier 8,200,000bxp_AmountOfEachTier
/ us-gaap_RangeAxis
= bxp_ThresholdMember
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_MYLTIPtwothousandfifteenMember		  
High [Member] | 2015 MYLTIP [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Amount of Each Tier 40,800,000bxp_AmountOfEachTier
/ us-gaap_RangeAxis
= bxp_HighMember
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_MYLTIPtwothousandfifteenMember		  
Maximum [Member] | 2015 MYLTIP [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Potential Awards Earned 40,800,000bxp_PotentialAwardsEarned
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_MYLTIPtwothousandfifteenMember		  
Minimum [Member] | 2015 MYLTIP [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Potential Awards Earned $ 0bxp_PotentialAwardsEarned
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_MYLTIPtwothousandfifteenMember		  
MYLTIP Vesting 2018 [Member] | 2015 MYLTIP [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Vesting Percentage 50.00%bxp_VestingPercentage
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_MYLTIPtwothousandfifteenMember
/ bxp_VestingPeriodAxis
= bxp_MyltipVesting2018Member		  
Vesting Date Feb. 04, 2018  
MYLTIP vesting 2019 [Member] | 2015 MYLTIP [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Vesting Percentage 50.00%bxp_VestingPercentage
/ bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis
= bxp_MYLTIPtwothousandfifteenMember
/ bxp_VestingPeriodAxis
= bxp_MYLTIPvesting2019Member		  
Vesting Date Feb. 04, 2019