Stock Option and Incentive Plan	3 Months Ended
Mar. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option and Incentive Plan	Stock Option and Incentive Plan On January 28, 2013, the Company's Compensation Committee approved multi-year long-term incentive program (MYLTIP) awards under the Company's 2012 Stock Option and Incentive Plan (the "2012 Plan") to officers and employees of the Company. MYLTIP awards utilize total return to shareholders ("TRS") over a three-year measurement period, on an annualized, compounded basis, as the performance metric. Earned awards will be based on the Company's TRS relative to (i) the Cohen & Steers Realty Majors Portfolio Index (50% weight) and (ii) the NAREIT Office Index adjusted to exclude the Company (50% weight). Earned awards will range from zero to a maximum of approximately $30.7 million depending on the Company's TRS relative to the two indices, with four tiers (threshold: approximately $5.1 million; target: approximately $10.2 million; high: approximately $20.5 million; exceptional: approximately $30.7 million) and linear interpolation between tiers. Earned awards measured on the basis of relative TRS performance are subject to an absolute TRS component in the form of relatively simple modifiers that (A) reduce the level of earned awards in the event the Company's annualized TRS is less than 2% and (B) cause some awards to be earned in the event the Company's annualized TRS is more than 10% even though on a relative basis alone the Company's TRS would not result in any earned awards. Earned awards (if any) will vest 25% on February 4, 2016, 25% on February 4, 2017 and 50% on February 4, 2018, based on continued employment. Vesting will be accelerated in the event of a change in control, termination of employment by the Company without cause, termination of employment by the award recipient for good reason, death, disability or retirement. If there is a change of control prior to February 4, 2016, earned awards will be calculated based on TRS performance up to the date of the change of control. MYLTIP awards are in the form of LTIP Units issued on the grant date which (i) are subject to forfeiture to the extent awards are not earned and (ii) prior to the performance measurement date are only entitled to one-tenth (10%) of the regular quarterly distributions payable on common partnership units. Under the Financial Accounting Standards Board's Accounting Standards Codification (“ASC”) 718 “Compensation-Stock Compensation” the MYLTIP awards have an aggregate value of approximately $8.1 million, which amount will generally be amortized into earnings over the five-year plan period under the graded vesting method. On March 11, 2013, the Company announced that Owen D. Thomas would succeed Mortimer B. Zuckerman as the Company's Chief Executive Officer, effective April 2, 2013. Mr. Zuckerman will continue to serve as Executive Chairman for a transition period and thereafter will continue to serve as the Non-Executive Chairman of the Board. In connection with succession planning, the Company and Mr. Zuckerman entered into a Transition Benefits Agreement to recognize his extraordinary services previously rendered and ensure a well-managed transition. If Mr. Zuckerman remains employed by the Company through July 1, 2014, he will be entitled to receive on January 1, 2015 a lump sum cash payment of $6.7 million and an equity award with a targeted value of approximately $11.1 million. The cash payment and equity award vest one-third on each of March 10, 2013, October 1, 2013 and July 1, 2014, subject to acceleration in certain circumstances. As a result, the Company recognized approximately $6.6 million of compensation expense during the three months ended March 31, 2013. In addition, the agreement provides that if Mr. Zuckerman terminates his employment with the Company for any reason, voluntarily or involuntarily, he will become fully vested in any outstanding equity awards with time-based vesting. As a result, during the three months ended March 31, 2013, the Company accelerated the remaining approximately $12.9 million of stock-based compensation expense associated with Mr. Zuckerman's unvested long-term equity awards. During the three months ended March 31, 2013, the Company issued 35,087 shares of restricted common stock, 201,373 non-qualified stock options, 153,006 LTIP Units and 280,000 2013 MYLTIP Units to employees and non-employee directors under the 2012 Plan. Employees and directors paid $0.01 per share of restricted common stock and $0.25 per LTIP Unit, OPP Unit and 2013 MYLTIP Unit. An LTIP Unit is generally the economic equivalent of a share of restricted stock in the Company. The aggregate value of the LTIP Units is included in noncontrolling interests in the Consolidated Balance Sheets. Grants of restricted stock and LTIP Units to employees vest in four equal annual installments. Restricted stock is measured at fair value on the date of grant based on the number of shares granted, as adjusted for forfeitures, and the closing price of the Company’s Common Stock on the date of grant as quoted on the New York Stock Exchange. Such value is recognized as an expense ratably over the corresponding employee service period. The shares of restricted stock granted during the three months ended March 31, 2013 were valued at approximately $3.7 million ($105.10 per share). The non-qualified stock options granted during the three months ended March 31, 2013 had a fair value on the date of grant of $18.64 per option, which was computed using the Black-Scholes option-pricing model utilizing the following assumptions: an expected life of 6.3 years, a risk-free interest rate of 1.19%, an expected price volatility of 26% and an expected dividend yield of 3%. The weighted-average exercise price of the options is $105.10, which was the closing price of the Company’s common stock on the date of grant. The LTIP Units granted during the three months ended March 31, 2013 were valued at approximately $14.8 million ($96.33 per unit fair value) using a Monte Carlo simulation method model. The per unit fair value of each LTIP Unit granted was estimated on the date of grant using the following assumptions: an expected life of 5.7 years, a risk-free interest rate of 1.03% and an expected price volatility of 26%. As the 2011 OPP Units, 2012 OPP Units and 2013 MYLTIP Units are subject to both a service condition and a market condition, the Company recognizes the compensation expense related to the 2011 OPP Units, 2012 OPP Units and 2013 MYLTIP Units under the graded vesting attribution method. Under the graded vesting attribution method, each portion of the award that vests at a different date is accounted for as a separate award and recognized over the period appropriate to that portion so that the compensation cost for each portion should be recognized in full by the time that portion vests. Dividends paid on both vested and unvested shares of restricted stock are charged directly to Dividends in Excess of Earnings in the Consolidated Balance Sheets. Aggregate stock-based compensation expense associated with restricted stock, non-qualified stock options, LTIP Units, 2011 OPP Units, 2012 OPP Units and 2013 MYLTIP Units was approximately $25.5 million and $10.9 million for the three months ended March 31, 2013 and 2012, respectively. For the three months ended March 31, 2013, stock-based compensation expense includes approximately $16.9 million consisting of the acceleration of the expense of the Company’s Executive Chairman’s stock-based compensation awards and the stock-based compensation awards associated with his transition benefits agreement related to the Company's succession planning. For the three months ended March 31, 2012, stock-based compensation expense includes approximately $2.7 million consisting of the acceleration of vesting of the Company’s Chief Operating Officer’s stock-based compensation awards associated with his resignation. At March 31, 2013, there was $23.9 million of unrecognized compensation expense related to unvested restricted stock and LTIP Units and $14.8 million of unrecognized compensation expense related to unvested 2011 OPP Units, 2012 OPP Units and 2013 MYLTIP Units that is expected to be recognized over a weighted-average period of approximately 3.1 years.

Stock Option and Incentive Plan

On January 28, 2013, the Company's Compensation Committee approved multi-year long-term incentive program (MYLTIP) awards under the Company's 2012 Stock Option and Incentive Plan (the "2012 Plan") to officers and employees of the Company. MYLTIP awards utilize total return to shareholders ("TRS") over a three-year measurement period, on an annualized, compounded basis, as the performance metric. Earned awards will be based on the Company's TRS relative to (i) the Cohen & Steers Realty Majors Portfolio Index (50% weight) and (ii) the NAREIT Office Index adjusted to exclude the Company (50% weight). Earned awards will range from zero to a maximum of approximately $30.7 million depending on the Company's TRS relative to the two indices, with four tiers (threshold: approximately $5.1 million; target: approximately $10.2 million; high: approximately $20.5 million; exceptional: approximately $30.7 million) and linear interpolation between tiers. Earned awards measured on the basis of relative TRS performance are subject to an absolute TRS component in the form of relatively simple modifiers that (A) reduce the level of earned awards in the event the Company's annualized TRS is less than 2% and (B) cause some awards to be earned in the event the Company's annualized TRS is more than 10% even though on a relative basis alone the Company's TRS would not result in any earned awards.

Earned awards (if any) will vest 25% on February 4, 2016, 25% on February 4, 2017 and 50% on February 4, 2018, based on continued employment. Vesting will be accelerated in the event of a change in control, termination of employment by the Company without cause, termination of employment by the award recipient for good reason, death, disability or retirement. If there is a change of control prior to February 4, 2016, earned awards will be calculated based on TRS performance up to the date of the change of control. MYLTIP awards are in the form of LTIP Units issued on the grant date which (i) are subject to forfeiture to the extent awards are not earned and (ii) prior to the performance measurement date are only entitled to one-tenth (10%) of the regular quarterly distributions payable on common partnership units.

Under the Financial Accounting Standards Board's Accounting Standards Codification (“ASC”) 718 “Compensation-Stock Compensation” the MYLTIP awards have an aggregate value of approximately $8.1 million, which amount will generally be amortized into earnings over the five-year plan period under the graded vesting method.

On March 11, 2013, the Company announced that Owen D. Thomas would succeed Mortimer B. Zuckerman as the Company's Chief Executive Officer, effective April 2, 2013. Mr. Zuckerman will continue to serve as Executive Chairman for a transition period and thereafter will continue to serve as the Non-Executive Chairman of the Board. In connection with succession planning, the Company and Mr. Zuckerman entered into a Transition Benefits Agreement to recognize his extraordinary services previously rendered and ensure a well-managed transition. If Mr. Zuckerman remains employed by the Company through July 1, 2014, he will be entitled to receive on January 1, 2015 a lump sum cash payment of $6.7 million and an equity award with a targeted value of approximately $11.1 million. The cash payment and equity award vest one-third on each of March 10, 2013, October 1, 2013 and July 1, 2014, subject to acceleration in certain circumstances. As a result, the Company recognized approximately $6.6 million of compensation expense during the three months ended March 31, 2013. In addition, the agreement provides that if Mr. Zuckerman terminates his employment with the Company for any reason, voluntarily or involuntarily, he will become fully vested in any outstanding equity awards with time-based vesting. As a result, during the three months ended March 31, 2013, the Company accelerated the remaining approximately $12.9 million of stock-based compensation expense associated with Mr. Zuckerman's unvested long-term equity awards.

During the three months ended March 31, 2013, the Company issued 35,087 shares of restricted common stock, 201,373 non-qualified stock options, 153,006 LTIP Units and 280,000 2013 MYLTIP Units to employees and non-employee directors under the 2012 Plan. Employees and directors paid $0.01 per share of restricted common stock and $0.25 per LTIP Unit, OPP Unit and 2013 MYLTIP Unit. An LTIP Unit is generally the economic equivalent of a share of restricted stock in the Company. The aggregate value of the LTIP Units is included in noncontrolling interests in the Consolidated Balance Sheets. Grants of restricted stock and LTIP Units to employees vest in four equal annual installments. Restricted stock is measured at fair value on the date of grant based on the number of shares granted, as adjusted for forfeitures, and the closing price of the Company’s Common Stock on the date of grant as quoted on the New York Stock Exchange. Such value is recognized as an expense ratably over the corresponding employee service period. The shares of restricted stock granted during the three months ended March 31, 2013 were valued at approximately $3.7 million ($105.10 per share). The non-qualified stock options granted during the three months ended March 31, 2013 had a fair value on the date of grant of $18.64 per option, which was computed using the Black-Scholes option-pricing model utilizing the following assumptions: an expected life of 6.3 years, a risk-free interest rate of 1.19%, an expected price volatility of 26% and an expected dividend yield of 3%. The weighted-average exercise price of the options is $105.10, which was the closing price of the Company’s common stock on the date of grant. The LTIP Units granted during the three months ended March 31, 2013 were valued at approximately $14.8 million ($96.33 per unit fair value) using a Monte Carlo simulation method model. The per unit fair value of each LTIP Unit granted was estimated on the date of grant using the following assumptions: an expected life of 5.7 years, a risk-free interest rate of 1.03% and an expected price volatility of 26%. As the 2011 OPP Units, 2012 OPP Units and 2013 MYLTIP Units are subject to both a service condition and a market condition, the Company recognizes the compensation expense related to the 2011 OPP Units, 2012 OPP Units and 2013 MYLTIP Units under the graded vesting attribution method. Under the graded vesting attribution method, each portion of the award that vests at a different date is accounted for as a separate award and recognized over the period appropriate to that portion so that the compensation cost for each portion should be recognized in full by the time that portion vests. Dividends paid on both vested and unvested shares of restricted stock are charged directly to Dividends in Excess of Earnings in the Consolidated Balance Sheets. Aggregate stock-based compensation expense associated with restricted stock, non-qualified stock options, LTIP Units, 2011 OPP Units, 2012 OPP Units and 2013 MYLTIP Units was approximately $25.5 million and $10.9 million for the three months ended March 31, 2013 and 2012, respectively. For the three months ended March 31, 2013, stock-based compensation expense includes approximately $16.9 million consisting of the acceleration of the expense of the Company’s Executive Chairman’s stock-based compensation awards and the stock-based compensation awards associated with his transition benefits agreement related to the Company's succession planning. For the three months ended March 31, 2012, stock-based compensation expense includes approximately $2.7 million consisting of the acceleration of vesting of the Company’s Chief Operating Officer’s stock-based compensation awards associated with his resignation. At March 31, 2013, there was $23.9 million of unrecognized compensation expense related to unvested restricted stock and LTIP Units and $14.8 million of unrecognized compensation expense related to unvested 2011 OPP Units, 2012 OPP Units and 2013 MYLTIP Units that is expected to be recognized over a weighted-average period of approximately 3.1 years.