Share and Unit-Based Plans:

9 Months Ended

Sep. 30, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Under the Long-Term Incentive Plan ("LTIP"), each award recipient is issued a form of operating partnership units ("LTIP Units") in the Operating Partnership. Upon the occurrence of specified events and subject to the satisfaction of applicable vesting conditions, LTIP Units (after conversion into OP Units) are ultimately redeemable for common stock of the Company, or cash at the Company's option, on a one-unit for one-share basis. LTIP Units receive cash dividends based on the dividend amount paid on the common stock of the Company. The LTIP may include both market-indexed awards and service-based awards. The market-indexed LTIP Units vest over the service period of the award based on the percentile ranking of the Company in terms of total return to the stockholders (the "Total Return") per common stock share relative to the Total Return of a group of peer REITs, as measured at the end of the measurement period.

On January 1, 2015, the Company granted 49,451 LTIP Units with a grant date fair value of $83.41 per LTIP Unit that will vest in equal annual installments over a service period ending December 31, 2017. Concurrently, the Company granted 186,450 market-indexed LTIP Units ("2015 LTIP Units") at a grant date fair value of $66.37 per LTIP Unit that vest over a service period ending December 31, 2015. The 2015 LTIP Units were equally divided between two types of awards. The terms of both types of awards were the same, except one award has an additional 3% absolute total stockholder return requirement, which if it is not met, then such LTIP Units will not vest. The fair value of the 2015 LTIP Units was estimated on the date of grant using a Monte Carlo Simulation model that assumed a risk free interest rate of 0.25% and an expected volatility of 16.81%.

On March 6, 2015, the Company granted 132,607 LTIP Units at a fair value of $86.72 per LTIP Unit that were fully vested on the grant date.

The following summarizes the compensation cost under the share and unit-based plans:



	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
	2015		2014		2015		2014
LTIP Units	$	3,812	$	3,465	$	22,810	$	25,133
Stock awards	28		84		225		281
Stock units	881		1,134		5,214		3,775
Stock options	4		4		12		12
Phantom stock units	248		296		827		902
	$	4,973	$	4,983	$	29,088	$	30,103

The Company capitalized share and unit-based compensation costs of $551 and $525 for the three months ended September 30, 2015 and 2014, respectively, and $5,459 and $4,886 for the nine months ended September 30, 2015 and 2014, respectively. Unrecognized compensation costs of share and unit-based plans at September 30, 2015 consisted of $7,940 from LTIP Units, $48 from stock awards, $4,251 from stock units, $31 from stock options and $135 from phantom stock units.

The following table summarizes the activity of the non-vested LTIP Units, stock awards, phantom stock units and stock units:



	LTIP Units				Stock Awards				Phantom Stock Units				Stock Units
	Units		Value(1)		Shares		Value(1)		Units		Value(1)		Units		Value(1)
Balance at January 1, 2015	46,695		$	58.89	9,189		$	59.25	9,269		$	58.35	144,374		$	59.94
Granted	368,508		75.98		—		—		7,056		80.68		76,531		86.61
Vested	(132,607	)	86.72		(7,410	)	58.65		(11,839	)	70.82		(84,498	)	61.14
Forfeited	—		—		—		—		(2,458	)	55.62		—		—
Balance at September 30, 2015	282,596		$	68.12	1,779		$	61.72	2,028		$	66.52	136,407		$	74.66


(1)	Value represents the weighted average grant date fair value.

The following table summarizes the activity of the stock appreciations rights ("SARs") and stock options outstanding:



	SARs				Stock Options
	Shares		Value(1)		Shares	Value(1)
Balance at January 1, 2015	772,639		$	56.67	10,068	$	59.57
Granted	—		—		—	—
Exercised	(344,981	)	56.88		—	—
Forfeited	—		—		—	—
Balance at September 30, 2015	427,658		$	56.50	10,068	$	59.57


(1)	Value represents the weighted average exercise price.